Tissue welding and cutting apparatus and methods

ABSTRACT

A surgical apparatus and methods for severing and welding tissue, in particular blood vessels. The apparatus includes an elongated shaft having a pair of relatively movable jaws at a distal end thereof. A first heating element on one of the jaws is adapted to heat up to a first temperature and form a welded region within the tissue, while a second heating element on one of the jaws is adapted to heat up to a second temperature and sever the tissue within the welded region. The first and second heating elements may be provided on the same or opposite jaws. A control handle provided on the proximal end of the elongated shaft includes controls for opening and closing the jaws, and may include an actuator for sending current through the first and second heating elements. The first and second heating elements may be electrically connected in series, and the first heating element may be bifurcated such that it conducts about one half of the current as the second heating element. A force-limiting mechanism provided either within the control handle, in the elongated shaft, or at the jaws limits the pressure applied to the tissue by the jaws to ensure that the tissue is severed and the ends effectively welded within a short amount of time.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/482,310, filed on Apr. 7, 2017 (now U.S. Pat. No. 10,856,927), whichis a divisional of U.S. patent application Ser. No. 14/551,599, filed onNov. 24, 2014 (now U.S. Pat. No. 9,636,163), which is a divisional ofU.S. patent application Ser. No. 13/494,985, filed on Jun. 12, 2012 (nowU.S. Pat. No. 8,894,638), which is a continuation of U.S. patentapplication Ser. No. 11/090,750, filed Mar. 25, 2005 (now U.S. Pat. No.8,197,472), the entire disclosures of which are each expresslyincorporated by reference herein. The present application also relatesto U.S. Pat. No. 7,918,848, issued on Apr. 5, 2011, the entiredisclosure of which is expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to surgical devices and methods forsevering and sealing blood vessels and, in particular, to an endoscopictissue welder.

BACKGROUND OF THE INVENTION

Endoscopic harvesting of vessels is well known in the surgical field andhas been the subject of a great deal of recent technologicaladvancement. Typically, the harvested vessel is used for bypass or as ashunt around an artery that has diminished flow from stenosis or otheranomaly, such as a Coronary Artery Bypass Grafting (CABG) procedure.Often in CABG, a saphenous vein from the patient's leg is harvested forsubsequent use in the surgery. Other vessels, such as the radial artery,can also be harvested and used in this manner. Vessel harvestinginvolves liberating the vessel from surrounding tissue and transectingsmaller side branches, cauterizing, tying or ligating the vessel at aproximal site and a distal site, and then transecting the vessel at bothsites before it is removed from the body.

Known endoscopic methods and devices for performing vessel harvestingare discussed in detail in U.S. Pat. No. 6,176,895 to Chin, et al., Re36,043 to Knighton, U.S. Pat. No. 6,406,425 to Chin, et al., and U.S.Pat. No. 6,471,638 to Chang, et al., all of which are expresslyincorporated herein by reference. Furthermore, various devices andmethods disclosed in U.S. Pat. No. 5,895,353 to Lunsford, et al., andU.S. Pat. No. 6,162,173 to Chin, et al., and pending patent applicationSer. No. 10/602,490 entitled “Apparatus and Method for Integrated VesselLigator and Transector” are also expressly incorporated herein byreference. Also, commercial vessel harvesting systems sold under thetradename VASOVIEW® Uniport Plus and VASOVIEW® 5 are available fromGuidant Corporation of Santa Clara, Calif.

Numerous instruments are known which coagulate, seal, join, or cuttissue, and which are suitable, for example, for severing a targetvessel from surrounding side branches and securing the separated ends tostanch bleeding. Such devices typically comprise a pair of tweezers,jaws or forceps that grasp onto and hold tissue therebetween. Thedevices may operate with a heating element in contact with the tissue,with an ultrasonic heater that employs frictional heating of the tissue,or with a mono- or bi-polar electrode heating system that passes currentthrough the tissue such that the tissue is heated by virtue of its ownelectrical resistance. The devices heat the tissue to temperatures suchthat the tissue is either “cut” or “sealed”, as follows. When tissue isheated in excess of 100° Celsius, the tissue disposed between thetweezers, jaws or forceps will be broken down and is thus, “cut”.However, when the tissue is heated to temperatures between 50° to 90°Celsius, the tissue will instead simply “seal” or “weld” to adjacenttissue. In the context of the present application, the term “tissuewelding” refers to procedures that cause otherwise separated tissue tobe sealed, coagulated, fused, welded or otherwise joined together.Numerous devices employing the same general principle of controlledapplication of a combination of heat and pressure can be used to join or“weld” adjacent tissues to produce a junction of tissues or ananastomosis of tubular tissues.

Monopolar and bipolar probes, forceps or scissors use high frequencyelectrical current that passes through the tissue to be coagulated. Thecurrent passing through the tissue causes the tissue to be heated,resulting in coagulation of tissue proteins. In the monopolar variety ofthese instruments, the current leaves the electrode and after passingthrough the tissue, returns to the generator by means of a “groundplate” which is attached or connected to a distant part of the patient'sbody. In a bipolar version of such an electro-surgical instrument, theelectric current passes between two electrodes with the tissue beingplaced or held between the two electrodes as in the “Kleppinger bipolarforceps” used for occlusion of Fallopian tubes. There are many examplesof such monopolar and bipolar instruments commercially available todayfrom companies including Valley Lab, Cabot, Meditron, Wolf, Storz andothers worldwide.

A new development in this area is the “Tripolar” instrument marketed byCabot and Circon-ACMI which incorporates a mechanical cutting element inaddition to monopolar coagulating electrodes. A similar combined sealingand mechanical cutting device may also be known as a tissue “bisector,”which merges the terms bipolar cautery and dissector. One tissuebisector is packaged for sale as an element of the VASOVIEW® UniportPlus and VASOVIEW® 5 vessel harvesting systems by Guidant Corporation ofSanta Clara, Calif.

In ultrasonic tissue heaters, a very high frequency (ultrasonic)vibrating element or rod is held in contact with the tissue. The rapidvibrations generate heat causing the proteins in the tissue to becomecoagulated.

Conductive tissue welders usually include jaws that clamp tissuetherebetween, one or both of which are resistively heated. In this typeof instrument, no electrical current passes through the tissue, as isthe case for monopolar or bipolar cautery. Some tissue welders alsoperform a severing function without a mechanical knife. For example, theThermal Ligating Shears made by Starion Instruments of Saratoga, Calif.is a, hand activated instrument that utilizes thermal welding tosimultaneously seal and divide soft tissue during laparoscopic generalsurgery procedures. The Starion device uses a heating element at the tipof one of a pair of facing jaws combined with pressure to denature theprotein molecules within the tissue. The denatured proteins bondtogether, forming an amorphous mass of protein, and fusing tissue layerstogether. The procedure can be used to fuse vessels closed. More highlyfocused heat may be applied in the center of the tissue within the jawsof the instrument, causing the tissue or vessel to divide, thusresulting in two sealed ends. A description of the Starion device isprovided at www.starioninstruments.com.

Despite accepted means for severing and securing vessels, such as in avessel harvesting procedure, there remains a need for an improved devicethat increases the operating efficiency of the device and ensures theleast amount of trauma to surrounding tissue while simultaneouslyproviding repeatable secure sealing of the severed vessel ends.

SUMMARY OF THE INVENTION

The present invention provides designs of tissue severing/sealingdevices that control heat distribution within the distal jaws. In oneembodiment, multiple heating elements are provided on one of the jaws ofa tissue welding device. A primary heating element is positioned alongthe midline of the jaw length and is electrically connected to twosecondary heating elements, one on each side of the primary heater.Electrical current passes through the primary heater and is then dividedequally between the two secondary heaters. The electrical resistances ofthe three heating elements are designed such that the primary heater hasthe highest power dissipation (i.e., reaches the highest temperature),while the two secondary heaters have equal power dissipation but lowerthan that of the primary heater. This has the effect that the primaryheater cuts tissue, while the secondary heaters seal or weld tissue. Thethree heating elements are separated by electrical insulation alongtheir working lengths to prevent inadvertent contact, for example an airgap, silicone, or other such insulation.

The present invention provides a surgical apparatus for welding andsevering tissue, comprising an elongated shaft having first and secondrelatively movable elongated jaws having jaw-facing surfaces attached toa distal end thereof. A first heating element for welding tissue and asecond heating element for severing tissue are provided on thejaw-facing surface of the first jaw. The first heating element isadapted to heat up to a first temperature upon application of power,while the second heating element is adapted to heat up to a secondtemperature greater than the first temperature upon application of powerso that the first heating element welds tissue while the second heatingelement cuts tissue. Desirably, the first heating element has a lowerelectrical resistance than the second heating element. Furthermore, thefirst heating element preferably has a wider profile than the secondheating element in a plane transverse to the direction of elongation ofthe first jaw. Preferably, the first heating element has a lower profilerelative to the second heating element in a direction toward the secondjaw.

In a preferred embodiment, the second heating element extends generallycentrally along the jaw-facing surface of the first jaw, and the firstheating element comprises at least two welding members, one each oneither side of the second heating element. The two welding members maybe formed by a bifurcated segment of a one-piece heating element, theseparated portions in the bifurcated segment being connected in parallelto a source of power. The first and second heating elements aredesirably connected in series to a common source of power such that acurrent passing through one of the pair of welding members is about onehalf the current passing through the second heating element. Preferably,each of the welding members comprises a strip of material having agenerally flat jaw-facing surface defining a lateral width, and thesecond heating element defines a cylindrical jaw-facing surface having alateral width smaller than that of either of the welding members.

The second jaw may not include heating elements such that the first jawis a “hot” jaw, and the second jaw is a “cold” jaw. A third heatingelement for welding tissue may also be provided on the jaw-facingsurface of the first jaw. The third heating element is adapted to heatup to a temperature that is also lower than the second temperature(i.e., lower than a cutting temperature), and desirably to the firsttemperature, upon application of power. Preferably, a control handle isconnected to a proximal end of the elongated shaft and has a controlactuator mounted thereon for alternately separating and bringingtogether the jaw-facing surfaces of the elongated jaws. A force-limitinginterface between the control actuator and the elongated jaws limits themagnitude of closing force of the jaws.

In accordance with one embodiment, the first jaw comprises a ceramicmaterial having a thermal conductivity of less than 5.0 W/m-K. Forexample, the first jaw may comprise an inner member covered with theceramic material. To reduce heat loss to the jaws, the inner member ofthe first jaw does not form a part of any electrical conduction pathleading to either the first or second heating elements. The apparatusmay further include a heat sink provided on the jaw-facing surface ofone of the first or second jaws and positioned to influence lines ofheat flux to remain within the jaws, and thermal insulation provided onthe outboard side(s) of the heat sink.

The present invention also provides a surgical apparatus for welding andsevering tissue, comprising first and second relatively movable elongatejaws having jaw-facing surfaces and an elongated shaft having the firstand second relatively movable jaws attached to a distal end thereof. Afirst heating element for welding tissue is provided on the jaw-facingsurface of one of the first or second jaws. A second heating element forsevering tissue is provided on the jaw-facing surface of one of thefirst or second jaws. An electrical circuit path within the surgicalapparatus includes a portion extending along the elongated shaft andthrough the first and second heating elements in series. Uponapplication of current through the electrical circuit path, the firstheating element heats up to a first temperature and the second heatingelement heats up to a second temperature greater than the firsttemperature, so that the first heating element welds tissue while thesecond heating element cuts tissue.

In one preferred embodiment, the second heating element is provided onthe jaw-facing surface of the second jaw, wherein the first heatingelement has a wider profile than the second heating element in a planetransverse to the direction of elongation of the first jaw. The firstheating element desirably has a lower electrical resistance than thesecond heating element. Preferably, a control handle is connected to aproximal end of the elongated shaft and has a control actuator mountedthereon for alternately separating and bringing together the jaw-facingsurfaces of the elongated jaws. A force-limiting interface between thecontrol actuator and the elongated jaws limits the magnitude of closingforce of the jaws.

Another aspect of the present invention is a surgical method of severinga target tissue while welding the severed ends. The method includesproviding a surgical apparatus for welding and severing tissue includinga pair of jaws adapted to open and close upon the target tissue, thejaws including first and second resistive heating elements. The jaws areclosed upon target tissue and the first heating element is energized toa first temperature and for a sufficient period of time to form a weldedregion in the target tissue. The second heating element is alsoenergized to a second temperature greater than the first temperature tosever the target tissue within the welded region. Preferably, step ofelectrically energizing the second heating element is performed afterforming the weld in the target tissue. In a useful application of thesurgical method, the target tissue is a target vessel, and the step ofclosing comprises transversely closing the jaws upon the target vessel.

A still further aspect of the present invention is a surgical apparatusfor welding and severing tissue, comprising first and second relativelymovable elongated jaws having jaw-facing surfaces. An elongated shaftsupports the first and second relatively movable the jaws at a distalend thereof. An energy applicator is provided on the jaw-facing surfaceof the first jaw. The first jaw comprises a ceramic material having athermal conductivity of less than 5.0 W/m-K to help reduce the amount ofheat generated by the energy applicator that is lost to the jaws. Thefirst jaw may consist essentially of the ceramic material, or mayinclude an inner member covered with the ceramic material. Preferably,the inner member of the first jaw does not form a part of any electricalconduction path leading to the energy applicator. The ceramic materialmay be selected from the group consisting of alumina; machinable glassceramic; zirconia; yttria; and partially stabilized zirconia.

Another aspect of the invention is a surgical apparatus for welding andsevering tissue, comprising an elongated shaft having first and secondrelatively movable elongated jaws having jaw-facing surfaces attached toa distal end thereof. A first heating element is provided on thejaw-facing surface of the first jaw, and is adapted to heat up to afirst temperature upon application of power. The first heating elementis made of or is placed in electrical series contact with a temperatureregulating material whose electrical resistance is not constant over apredetermined temperature range including the first temperature. In oneembodiment, the temperature regulating material is a PositiveTemperature Coefficient of Resistance (PTCR) material having anelectrical resistance that will increase with increasing temperaturesuch that the rate of temperature increase upon application of powerslows down as the temperature of the temperature regulating materialnears the first temperature. In an alternative embodiment, thetemperature regulating material is a Polymer Positive TemperatureCoefficient (PPTC) material having an electrical resistance that rapidlyincreases as the temperature of the temperature regulating materialnears the first temperature. The apparatus may include a circuit thatloops through the first heating element and through a device made of thetemperature regulating material. In one exemplary construction, thetemperature regulating material is formed into a rod-like element whichis surrounded by a tubular layer of electrical insulation, and whereinthe first heating element comprises an outer tube closely surroundingthe electrical insulation.

In accordance with a still further aspect, a surgical apparatus forwelding and severing tissue, comprising an elongated shaft having firstand second relatively movable elongated jaws having jaw-facing surfacesattached to a distal end thereof. An energy applicator for weldingtissue is provided on the jaw-facing surface of the first jaw, and afasciotomy cutter is provided on one of the jaws. For example, thefasciotomy cutter comprises a knife blade on an exterior surface of oneof the jaws. Alternatively, the energy applicator comprises a firstheating element for welding tissue provided on the jaw-facing surface ofthe first jaw and adapted to heat up to a first temperature uponapplication of power, and the fasciotomy cutter comprises an extensionof the first heating element that wraps around a distal tip of the firstjaw. The first jaw may comprise a longitudinal main portion and a slopeddistal end and wherein the first heating element extends along the mainportion and then slopes downward to the distal end. In thisconstruction, the fasciotomy cutter comprises a narrowed portion of thefirst heating element at the sloped distal end of the first jaw.Desirably, the sloped distal end of the first jaw comprises a pronouncedrib around which the first heating element conforms. Alternatively, thefasciotomy cutter comprises a heating element provided on one of thejaws and supplied with power through a different circuit than the energyapplicator.

Another aspect of the invention is a surgical apparatus for welding andsevering tissue, comprising first and second relatively movable elongatejaws having jaw-facing surfaces that are provided on the distal end ofan elongated shaft. An energy applicator for welding tissue is providedon the jaw-facing surface of the first jaw, and a resistance welder isprovided on one of the jaws. In accordance with one embodiment, theenergy applicator comprises a first heating element for welding tissueprovided on the jaw-facing surface of the first jaw and adapted to heatup to a first temperature upon application of power, and the resistancewelder comprises an extension of the first heating element that wrapsaround a distal tip of the first jaw. Preferably, the resistance welderhas a surface area per length that is larger than the surface area perlength of the first heating element for welding tissue. Alternatively,the resistance welder comprises a heating element provided on one of thejaws and supplied with power through a different circuit than the energyapplicator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are perspective views of a modular handle unit of a vesselharvesting system including a sled/adapter that permits a multipurposehandle base of the system to receive a tissue severing/welding device ofthe present invention;

FIGS. 2A-2B are perspective views of the distal end of an exemplarytissue severing/welding device of the present invention showing a pairof clamping jaws in their closed position;

FIGS. 3A-3B are perspective views of the distal end of the tissuesevering/welding device of FIGS. 2A-2B showing the clamping jaws intheir open position;

FIG. 4 is an exploded perspective view of the distal end of the tissuesevering/welding device of FIGS. 2A-2B;

FIGS. 5A-5B are perspective views of a “hot” jaw used in the exemplarytissue severing/welding device of the present invention;

FIGS. 6A-6B are enlarged perspective views of a proximal subassembly ofthe “hot” jaw of FIGS. 5A-5B;

FIGS. 7A-7C are perspective views of an exemplary heating elementsubassembly of the “hot” jaw of FIGS. 5A-5B;

FIGS. 8A-8H are perspective, plan, and elevational views of an exemplaryinner jaw forming a portion of the “hot” jaw of FIGS. 5A-5B;

FIGS. 9A-9E are perspective, plan, and elevational views of an exemplaryheating element for welding tissue used in the “hot” jaw of FIGS. 5A-5B;

FIGS. 10A-10H are perspective, plan, and elevational views of anexemplary boot for covering the inner jaw of FIGS. 8A-8H;

FIG. 11A is a perspective view of a proximal control handle of anexemplary tissue severing/welding device of the present invention;

FIGS. 11B-11C are opposite longitudinal sectional views of the controlhandle of FIG. 11A including a passive smoke filter therein;

FIGS. 11D-11F illustrate control handles having alternative smoke filterconfigurations;

FIG. 12 is a perspective exploded view of the proximal control handle ofFIG. 11A;

FIG. 13A is a perspective view of an alternative control handle of thepresent invention;

FIGS. 13B-13C are opposite longitudinal sectional views of the controlhandle of FIG. 13A;

FIGS. 14A-14C are elevational views of pair of jaws in open and closedpositions that illustrate a preferred jaw opening mechanism of thepresent invention;

FIG. 15 illustrates in cross-section a “hot” jaw spaced from a “cold”jaw similar to those shown in FIGS. 5A-5B;

FIGS. 16A-16B show variations on the “hot” jaw of FIG. 15;

FIG. 17 illustrates another possible variation on a hot jaw of thepresent invention having only one heating element and a conductive platefor absorbing heat and welding tissue;

FIGS. 18A-18C illustrate alternative jaw configurations in cross-sectionthat again includes multiple heating elements distributed on both jaws;

FIGS. 19A-19E illustrate an exemplary jaw including an inner jaw of alow thermal conductivity material;

FIG. 20 illustrates a longitudinal cross-section of a “hot” jaw of theprior art;

FIGS. 21A-21E illustrate a number of alternative jaw cross-sections thatreduce the amount of heat lost to the inner jaw;

FIGS. 22A and 22B schematically illustrate two different sets of jawshaving tissue clamping plates thereon and either a single or dualheating elements electrically connected in parallel;

FIG. 23 illustrates another sample test set up with a single heater on alower jaw and no heater on an upper jaw;

FIGS. 24A-24C illustrate three different alternative embodiments oftissue welding jaws that incorporate a material within the boots andadjacent the heating element that provide a “hot zone” for welding;

FIG. 25 illustrates a still further alternative embodiment of thepresent invention with multiple heating elements concentrically arrangedin a hot jaw;

FIGS. 26A and 26B are schematic views of an exemplary tissue welderhaving a fasciotomy cutter;

FIG. 27 is a side elevational view of the distal tips of upper and lowerjaws having a fasciotomy heater wire on a leading edge and angled towardone another such that when the jaws are closed they guide the faciatoward the heater wire;

FIG. 28 illustrates a pair of tissue welding jaws having a fasciotomycutter comprising a knife edge or blade longitudinally disposed on amidline of an outer surface of one of the jaws;

FIG. 29 is a graph of the temperature of a tissue welder heating elementover time;

FIG. 30 is a curve of the electrical resistance of a Polymer PositiveTemperature Coefficient (PPTC) device versus temperature;

FIGS. 31A and 31B schematically illustrate a circuit having a heatingelement and a PPTC device electrically connected in series therewith;

FIGS. 32A and 32B illustrate a rod-like PPTC element concentricallyarranged within an outer tubular heating element with a tubular layer ofelectrical insulation therebetween;

FIGS. 33A-33C illustrate a system which actively monitors and controlsthe temperature of tissue within the jaws of the thermal tissue weldingdevice of the present invention; and

FIGS. 34A, 34B, 35A, 35B, 36A, 36B and 37 illustrate a number of designsof tissue welder jaws having localized heaters on the distal end of oneof the jaws.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to one aspect of the present invention devices and methods forsealing, or coagulating, and severing tissue during surgery areprovided. The instruments incorporate means for controllably heatingtissue while simultaneously applying a definite and controllable amountof pressure to the tissue being heated. Because of the combinedapplication of heat and pressure, tissue proteins will become coagulatedand blood vessels within the tissue will be sealed shut, achievinghemostasis. Optimal sealing or coagulating tissue means producing astrong and durable seal or coagulation or anastomosis with a minimalamount of collateral tissue damage.

One aspect of the present invention includes a method and system for thesurgical treatment of biological tissue, wherein thermal energy andpressure are applied simultaneously, substantially simultaneously,consecutively, or alternatively, over a time such that tissue proteinsare denatured and the tissue will adhere or join to itself or to othertissues, for the purpose of coagulating bleeding, sealing tissue,joining tissue and cutting tissue. The minimum amount of heat or thermalenergy needed to accomplish these goals is expended, so as to minimizethermal damage to tissue adjacent to the treated site.

The devices of the invention may also incorporate means for cutting, orsevering the tissue. “Severing” includes dissecting or tissue division,tissue disruption or separation, plane development, or definition, ormobilization of tissue structures in combination with a coagulation, orhemostasis or sealing of blood vessels or other tissue structures suchas lymphatics, or tissue joining. Severing can be achieved by use ofamounts of heat greater than the amount required to coagulate thetissues, yet a minimum amount of energy is used with the least amount ofunwanted tissue necrosis. In conjunction with some aspect of theinvention, severing can be achieved by other mechanical, ultrasonic, orelectronic means, including, but not limited to, shearing action, laserenergy, and RF, or a combination of two or more of the above. Forexample, a blade may be passed through the coagulated tissue while thetissue is being held in the jaws of the instrument.

The present invention desirably provides a tissue welder that can beincorporated as a component of an integrated vessel harvesting system,such as is disclosed in application Ser. No. 10/951,426, filed Sep. 28,2004, which is expressly incorporated herein by reference. The vesselharvesting system is especially useful in minimally invasive endoscopicharvesting of blood vessels, including harvesting of internal thoracicartery, or vessels of the extremities along the radial artery in the armfor use in coronary artery bypass grafting, and the saphenous vein inthe leg for use in both coronary artery bypass grafting and peripheralartery bypass. In this context, the tissue welder performs both asevering and securing/welding function in separating side branches fromthe target vessel that is being harvested. It should be understood,however, that various aspects of the tissue welder described herein maybe utilized in conjunction with other surgical systems for coagulatingand/or dissecting tissue.

The exemplary embodiment of the tissue welder of the present inventioncomprises a so-called “welding and severing device” that is used toclose off and separate side branches from a primary vessel beingharvested, and also possibly to sever the primary vessel. However, thedevice is disclosed herein are suitable for welding and severing tissuein general not just vessels. In its broadest sense, the term tissuewelding and severing device refers to any and all devices thataccomplish a single function or any combination of the functions ofwelding, ligating, cauterizing, coagulating and/or sealing, and severingor transecting target tissue. For example, electrocautery tools such asbipolar scissors (or other plural electrode-based devices), monopolardevices, tissue bisectors, or other such devices provide these functionsalone or in conjunction with an integral blade or cutter. Other similardevices using various acceptable sources of energy for sealing thetissue (for example, RF, microwave, laser, ultrasound, direct thermalenergy, etc.) are also within the scope of the present invention. Eachdevice that acts on tissue to either weld or sever it will be termed anenergy applicator. The welding and severing device could be a singletool or a combination of plurality of separate tools each having its ownfunction useful in tissue severing, or more specifically in vesselharvesting.

Parenthetically, it is important to note that, while each of the variousaspects of the present invention may be used to advantage in combinationwith the other aspects, each is believed to also be of patentablesignificance when used alone with otherwise conventional systems andtechniques. Thus, the tissue welding devices and methods may beimplemented using heating and control structures other than thosedisclosed herein, and in the context of systems other than those forvessel harvesting. Furthermore, various aspects of the tissue welderdisclosed herein may be utilized with other welding and severingdevices, such as bipolar scissors or tissue bisectors. Similarly,certain aspects of the coagulation function of the tissue welder may becombined with a mechanical cutter to provide the severing function.

Finally, it should be understood that the exemplary and/or alternativetissue welders and features described herein have numerous applicationsin addition to vessel harvesting. For example, a tissue welder may beutilized in gastric bypass surgery to resect and close a portion of thestomach. Similarly, volume reduction of the lungs in patients withemphysema can also be accomplished with the devices disclosed herein.Bowel resection is another potential application. Other surgicalprocedures include: femoral popliteal bypass; severing/ligatingepigastric arteries for gastric reflux disease; fallopian tube ligation;vasectomies; severing/ligating arteries, veins, and bile ducts ingallbladder removal surgery; and nephrectomies where the ureters leadingto the kidney are transected and ligated.

FIGS. 1A-1C illustrate a modular handle unit 20 of an exemplary vesselharvesting system comprising a mating handle base 22 and handle sled 24.The handle base 22 includes a distal flange 26 secured to an elongatedcannula 28. The cannula 28 is sized to extend into a body cavity andprovides a channel for various vessel harvesting tools. The handle sled24 includes structure for mating with the handle base 22, as seen inFIG. 1A. Various modular handle units and vessel harvesting systems areillustrated and described in aforementioned application Ser. No.10/951,426, filed Sep. 28, 2004.

In the particular embodiment of FIGS. 1A-1C, the handle sled 24 providesan adapter for multipurpose handle bases common to a number of vesselharvesting systems, such that a tissue welding and severing device 30 ofthe present invention may be used for vessel harvesting within thesystem. Specifically, the handle sled or adapter 24 provides a port 32leading to an internal angled channel 34 through which the elongatedshaft 36 of the welding and severing device 30 may extend. The handlebase 22 and handle sled 24 couple such that the elongated shaft 36 isguided through the distal flange 26 and harvesting cannula 28. The finalassembly as seen in FIG. 1C shows that some of the movement controls forthe harvesting tools are located on the handle unit 20, while rotationof the welding and severing device 30 is accomplished by manipulatingthe entire handle 38 relative to the sled 24 with a second hand.

FIG. 1C also illustrates an enlarged distal end of the cannula 28through which a distal end of the tissue severing/welding device 30projects. The device 30 comprises a pair of relatively movable elongatedjaws 40, 42 on its distal end, which are shown open. Preferably, amechanism within the handle 38 includes an actuator 44 for opening andclosing the jaws 40, 42. The jaws 40, 42 are elongated generally in aproximal-distal direction such that they are much longer in thatdirection than in either orthogonal or transverse axis.

It should be understood that the term “jaw” refers to a member that maybe brought together with another similar member or other structure suchthat jaw-facing surfaces on both members are brought into contact orclose proximity. A jaw may be provided on a clamp, tweezers, forceps, orsimilar grasping tools. The jaws 40, 42 are mounted such that theirproximal ends are journalled about common or different but closelyspaced pivots and their distal ends open and close. Of course, the jawsmay be mounted for parallel movement instead of in a pivoting action. Anexemplary embodiment of the present invention includes a “hot” jaw and a“cold” jaw, the difference being that only one jaw is actively heated.It should be emphasized, however, that certain aspects of the presentinvention are applicable to different jaw configurations, such as bothbeing “hot” jaws, or both being “cold” jaws with a separate source ofheat.

In a preferred embodiment, the first jaw 40 comprises a “hot” jaw, whilethe second jaw 42 is a “cold” jaw. The term “hot” refers to the presenceof at least one active heating element thereon, while a “cold” jawprovides no active heating (but may become hot from indirect heating bythe other jaw). In the illustrated embodiment, as seen in FIG. 1C, thefirst or “hot” jaw 40 includes a first heating element 46 for weldingtissue and a second heating element 48 for severing tissue. The firstheating element 46 is adapted to heat up to a first temperature uponapplication of current therethrough, while the second heating element 48is adapted to heat up to a second temperature upon application ofcurrent therethrough which is greater than the first temperature.Conventional understanding is that when vascular tissue is heated inexcess of 100° C., the tissue will be broken down and is thus, “cut”.However, when vascular tissue is heated to temperatures between 50 to90° C., the tissue will instead simply “seal” or “weld” to adjacenttissue.

Various means are described herein for ensuring that the first heatingelement 46 heats up to within a welding temperature zone but not to acutting temperature threshold, while the second heating element 48 heatsup past the welding temperature zone into the cutting temperature zone.For example, the relative electrical resistance values of the first andsecond heating elements 46, 48 may be such that they heat up todifferent temperatures. Alternatively, the materials used may be thesame, but the first and second heating elements 46, 48 may be shaped ina manner that causes their differential heating. Still further, thecurrent passed through the two heating elements may be unequal.

FIG. 1C also basically illustrates a preferred configuration of the jaws40, 42 and a distal end of the shaft 36 extending through a distal endof the elongated cannula 28. In particular, the jaws 40, 42 are arrangedto pivot apart about a common axis, represented by pivot pin 50. Anexemplary mechanism for opening and closing the jaws 40, 42 will bedescribed in detail below. Each of the jaws 40, 42 includes an inner jawmember of rigid material and a boot 52 a, 52 b (as seen in FIG. 3A)surrounding the inner jaw member that is made of the material thatresists tissue adhesions during operation of the device. In oneembodiment, the inner jaw members are made of stainless steel, but othermaterials that provide less of a heat sink may be used. Preferably, theboots 52 a, 52 b are made of a heat-resistant silicone rubber. The boots52 a, 52 b also provide some thermal insulation around the inner jawmembers to reduce heat losses thereto. The first and second heatingelements 46, 48 are arranged external to the boot 52 a on the first jaw40, in particular on a surface of the jaw that faces the other jaw.

FIGS. 2-7 provide a number of assembled, exploded, and other partialviews of the distal end of an exemplary tissue welding and severingdevice 30 of the present invention. In FIGS. 2A-2B, the jaws 40, 42 areshown closed at the distal end of the welding and severing device 30.The device 30 includes a generally tubular distal tip 54 that fits onthe end of the device shaft 36 and houses a mechanism (described below)for opening and closing the jaws 40, 42. Both jaws 40, 42 exhibit ashallow curvature along their lengths such that their jaw-facingsurfaces contact along a curved line. In a preferred embodiment, theentire distal assembly of the device 30 including the jaws 40, 42 issized to fit through a 5 mm diameter port, thus enabling use inminimally invasive surgery.

The jaws 40, 42 preferably incorporate a multiple heater welding systemon a “hot” jaw 40. At a minimum, at least two heating element areprovided, with one heating element adapted to sever tissue and a secondheating element adapted to weld or coagulate tissue. In an exemplaryembodiment, the jaw 40 incorporates a “tri-heater” arrangement with oneheating element for cutting and two heating elements for weldingdisposed on either side of the cutter. Desirably, the heating elementsextend longitudinally from a proximal to a distal end of the jaw 40,with the cutter generally centrally located and the two welderssymmetrically located on either side.

FIGS. 3A-3B illustrate the jaws 40, 42 in their open configuration. Ascan be seen in FIG. 3B, the first heating element 46 is preferablybifurcated into two welding members separated laterally, with a singlesecond heating element 48 provided therebetween. The bifurcated weldingmembers of the first heating element 46 each provide a weld regionwithin the tissue, while the second heating element 48 cuts the tissuewithin the weld region. Technically, therefore, the hot jaw 40 includesthree heating elements: a central cutting element and two adjacentwelding elements. Although the exemplary embodiment combines the twoadjacent welding elements in a single piece, they could easily beconstructed separately. As mentioned above, one or both jaws 40, 42include inner jaw members surrounded by a boot 52 a, 52 b. The boot 52 baround the second jaw 42 is preferably provided with a series of lateralserrations 60 that facilitate gripping and prevent slipping of thetissue when clamped between the jaws. Because of the presence of thefirst and second heating elements 46, 48 on the exterior of the boot 52a on the first jaw 40, no serrations are necessary.

FIG. 4 shows the components of the distal end of the device 30 exploded,while FIGS. 5-7 best illustrate the specific shapes and subassembly ofthe first and second heating elements 46, 48, and how they mount on andcooperate with the first jaw 40. The inner jaw member 62 (seen isolatedin FIGS. 8A-8H) of the first or “hot” jaw 40 comprises an elongated andcurved distal portion 64 and a proximal pivot housing 66, includingthrough holes for pivotal movement with respect to the other jaw. Morespecifically, the proximal pivot housing 66 of the inner jaw member 62includes a large circular through hole 67 and an angled slot 68, bothformed in an outer wall section 69. A pair of sidewalls 70 upstandingfrom the outer wall section 69 provide a space on the inner side of thepivot housing 66 within which electrical wires and a pivot mechanism arereceived, as explained below.

The first heating element 46 comprises a proximal crimp 72 and flange73. Two elongated welding members 74 extend from the proximal crimp andflange in a distal direction and curl back upon themselves to terminateat a common barb 75 (see FIG. 7B). The elongated welding members 74preferably comprise thin, rectangular strips each having a lateral widthW that extend in parallel across a spaced distance S. Because thewelding members 74 are connected at their proximal ends by the crimp 72and flange 73 structure, and at their distal ends by the common barb 75,they define a bifurcated portion of the first heating element 46. In apreferred embodiment, the first heating element 46 comprises a single,homogeneous piece of metal (e.g., stainless steel) that has been formedinto the illustrated shape by stamping, bending, machining, etc.

The second heating element 48 extends between and in parallel with thespaced welding members 74 and is separated therefrom by air gaps. Theheating element 48 also extends in a distal direction the same length asthe welding member 74 and curls back upon itself to terminate at aconnection end 76 adjacent the barb 75 (see FIG. 7B). The connection end76 and barb 75 are electrically connected using a resistance or spotweld, for example. In the context of the present application, the term“resistance weld” used to describe the joint between two mechanicalparts encompasses all suitable varieties of such joints, including forexample, spot welds, laser welds, soldered joints, brazed joints, etc.

As seen in the exploded view of FIG. 4, the heating element 48 maycomprise an elongated wire or rod, and the connection end 76 may beformed by a separate U-shaped coupling 77 forming a series extensionthereon. The second heating element 48 has a raised profile relative tothe first heating element 46 in a direction toward the second jaw 42.This enhances the differential ability of the second heating element 48to cut through tissue while the first heating element 46 welds.Furthermore, the strip-like welding members 74 of the first heatingelement 46 each have flat jaw-facing surfaces, while the second heatingelement 48 defines a cylindrical jaw-facing surface having a lateralwidth smaller than that of either welding member.

An exemplary first heating element 46 is seen isolated in FIGS. 9A-9E.These illustrations show a heating element 46 that is slightly differentthan the one shown in preceding figures, although either may be usedwith good results. The difference is in the distal end which exhibits aflange 78 that is bent, for example, at 90.degree. instead of curlingback into the barb 75 toward the proximal end. The flange 78 is forkedto define a generally semi-circular opening 80 that receives the secondheating element 48. Although not shown, in this version the secondheating element 48 curls 180.degree. into the opening 80 and is securedin electrical contact therewith using a resistance weld, for example.

Now with specific reference to FIGS. 5-7, the heating elements 46, 48are shown having conductor wires attached thereto to form a seriescircuit. As seen in FIGS. 6B and 7A, a pair of insulated conductor wires82, 84 form part of a circuit path through the heating elements 46, 48.The first conductor wire 82 is in electrical communication with thefirst heating element 46 by virtue of a resistance weld at the proximalcrimp 72, while the second conductor wire 84 is in electricalcommunication with the second heating element 48. An insulated sleevearound the second conductor wire 84 extends through an aperture formedin the flange 73 of the first heating element 46. The barb 75 andconnection end 76 are electrically connected such that the first andsecond heating element 46, 48 define a current loop all along the lengthof the jaw 40.

Current through the conductors 82, 84 therefore passes in series throughthe first and second heating elements 46, 48. Current through the twoheating elements 46, 48 remains separated to the common distal endthereof, and in particular to the resistance weld between the barb 75and connection end 76. Because of the bifurcation of the first heatingelement 46 into the separate welding members 74, each of the weldingmembers 74 conducts in parallel approximately half of the current thatpasses through the second heating element 48. It should be understood,therefore, that if the heating elements are identical in shape andmaterial, each welding member 74 would heat up to a temperature lessthan that which the second heating element 48 attains because of thesplit current. This differential helps ensure that the first heatingelement 46 reaches the welding zone temperatures, while the secondheating element 48 reaches temperatures within the cutting zone. In theillustrated embodiment, the separate welding members 74 each have awider profile (i.e., larger surface area) facing the tissue in a planetransverse to the direction of elongation of the jaw 40 than does thesecond heating element 48. This structural difference in conjunctionwith the lower current and thus lower temperature helps facilitate awelding action on the tissue as opposed to a cutting action, in contrastto the central heating element 48 which is both narrower and hotter (andraised up higher).

Advantageously, however, the second heating element 48 is constructed soas to have a higher electrical resistance than either of the weldingmembers 74, and therefore even more of the already larger currentdissipates as heat. This combined phenomena of higher current and higherresistance causes the second heating element 48 to heat up to a cuttingtemperature zone, while the first heating of the 46 only reachestemperatures in the tissue welding zone. In a preferred embodiment, thefirst heating element 46 is made of a suitable conductive metal such as301 stainless steel, while the second heating element 48 comprises atube of rigid material with filler having a higher magnitude ofelectrical resistance than the tube, the combination having anelectrical resistance greater than stainless steel. In one specificembodiment, the tube is made of a nickel-chromium alloy such as INCONEL625 and is filled with an electrically insulating but thermallyconductive ceramic such as magnesium oxide (MgO) powder. Consequently, agreater current density passes through the hollow tube than if it weresolid, and therefore the material reaches a higher temperature at anygiven current. Additionally, the inner thermally conductive ceramic doesnot unduly restrict conductive heat flow through the element 48.Preferably, the second heating element 48 has a relatively highresistance of about 0.2 Ohms, and the entire system of the first andsecond heating elements has an average resistance of about 0.72 Ohms,and preferably less than 0.8 Ohms.

It is important to understand that the present invention contemplates atleast one cutting element and at least one welding element, electricallyconnected in series or not. For example, the illustrated embodiment maybe modified by utilizing two current paths, one for the first (welding)heating element 46 and one for the second (cutting) heating element 48.Alternatively, one cutting element and a single (i.e., not bifurcated)welding element may be provided on the hot jaw, both forming a part of acommon current path. Finally, the same arrangement can be utilized withseparate current paths. Moreover, as mentioned above, the cuttingelement may be provided on one jaw while the welding element is providedon the opposite jaw. In each of these alternative configurations, thecommon denominator is that upon application of a common or separatecurrents, the cutting element reaches a higher temperature than thewelding element.

FIGS. 10A-10H show a number of views of an exemplary boot 52 a used onthe “hot” jaw 40. As mentioned above, the boot 52 a is made of materialsuch as silicone rubber that resists tissue adhesions, and thusfacilitates multiple tissue severing/welding operations prior to areduction in the effectiveness of the jaws because of such tissueadhesions. The boot 52 a provides electrical insulation between theheating elements 46, 48, and also provides thermal insulation, thushelping to retain heat to the space between the jaws as opposed to beinglost to the often metallic inner jaws 62. The boot 52 a generallycomprises a hollow sleeve having an open proximal end 86 and a partiallyclosed distal end 88. An upper surface 90 that faces the cold jaw 40when the boot 52 a is mounted on the hot jaw 40 includes a pair oflongitudinally-oriented rails 92. As seen in FIGS. 10D and 10G, therails 92 are generally evenly spaced apart and provide guide channelsfor the bifurcated first heating element 46 and the central secondheating element 48. The distal end 88 of the boot 52 a has an openinginto which extend the joined and curled or bent distal ends of the twoheating elements 46, 48. This holds the distal ends of the twoelectrodes on the hot jaw 40. It should be noted that the distal end ofthe inner jaw member 62 has a forked depression as seen at 93 in FIG.7C. The insulating boot 52 a is molded so that it has an inside shapewhich conforms within this depression 93, and also provides an outwardlyopening cavity to receive the joined barb 75 and connection end 76. Thearrowhead shape of the barb 75 helps secure the heating elements inplace with respect to the soft insulating boot 52 a, which, again, ispreferably silicone rubber.

FIGS. 5-6 illustrate the integration of the combined heating elements46, 48 and conductor wires 82, 84 into the inner jaw member 62. As seenbest in FIG. 6B, the proximal crimp 72 secures the first heating element46 and an extension of the silicone boot 52 a to an upstanding flange 94of the pivot housing 66. The conductor wires 82, 84 are routed throughthe space in the pivot housing 66 formed by the pair of sidewalls 70.The first conductor wire 82 extends straight along one side wall 70 andis resistance welded or otherwise secured to the proximal crimp 72 ofthe first heating element 46. The second conductor wire 84 follows abent path along the other side wall 70 and passes through theaforementioned aperture formed in the proximal flange 73 of the firstheating element 46, as seen in FIG. 6A. FIG. 5B shows a bushing 96having an upstanding shaft stub 98 assembled over the pivot housing 66.The bushing 96 forms a part of a mechanism for opening and closing thejaws 40, 42, and will be more clearly described below.

One aspect of the present invention that facilitates assembly and thusreduces fabrication cost, is the integrated nature of the heatingelement subsystem. The subsystem is seen in FIGS. 6B and 7A, andconsists of five parts: the first heating element 46, the second heatingelement 48, the pivot housing 66 (typically fabricated integral with thefirst inner jaw 62), and the two wires 82 and 84 that provide currentthrough the series heating elements. These five parts are held togetherwith several crimps, or desirably resistance welds, or both, and may beeasily assembled prior to integration with the rest of the hot jaw 40.

As mentioned above, either or both of the jaws 40, 42 includes an innerjaw member covered with a boot. The exploded view of FIG. 4 shows boththe inner jaw member 62 of the hot jaw 40, and an inner jaw member 102of the second or “cold” jaw 42, along with the associated boots 52 a, 52b. Both boots 52 a, 52 b fit over and surround the curved distalportions of the inner jaw members 62, 102, respectively.

In prior tissue welders, stainless steel inner jaw members wereconveniently used as the return conduction path for the current passingthrough one or more electrodes. This had a distinct disadvantage in thatsome of the current was dissipated as resistance heat generated withinthe inner jaw member. This also had a disadvantage of heat conductionfrom heating element into jaw that resulted in less efficient energydelivery to tissue and potential inadvertent thermal injury. In oneaspect the present invention not only physically decouples the heatingelements 46, 48 from the first inner jaw member 62, in that a layer ofthe insulating boot 52 a is interposed therebetween, but no current runsthrough the inner jaw member. The series connection between the distalbarb 75 and connection end 76 means that the entire electricalconduction path along the hot jaw runs only through the heating elements46, 48. In this way, the efficiency of conversion of electrical energyinto desirable resistance heat is maximized, and the footprint of thedevice on tissue other than that directly in contact with the heatingelements is minimized.

In addition to being able to weld and sever tissue, and in particularblood vessels, the jaws 40, 42 may also be capable of performingfasciotomy, or an incision through fascia (e.g., bands or fillets offibrous tissue that separate different layers of tissue). As seen bestin FIG. 3B, where the jaws 40, 42 are shown open, the second heatingelement 48, the “cutter wire,” extends the full-length of the jaw alongits midplane. In addition, it is positioned so as to be raised upwardfrom the surrounding weld members of the first heating element 46 andthus presents the first surface of the hot jaw 40 to contact tissuereceived within the jaws. Fasciotomy can be performed by merely pushingthe open jaws through a band of tissue with the second heating element48 energized such that it cuts the tissue by heating it above thecutting temperature. Of course, in the exemplary embodiment the firstheating element 46 also heats up, although this will have negligibleimpact on the fasciotomy procedure.

FIG. 4 also illustrates a tapered tip 103 on the distal end of the innerjaw member 102 of the second or “cold” jaw 42. This tip 103 helpsfacilitate blunt dissection of tissue when the device is used as such.The surrounding boot 52 b will have a similar taper. In a preferredembodiment, the inner jaw member 102 has a generally rectangularcross-section, and the tip 103 has two tapers provided on the oppositestraight sides. Of course, other arrangements such as a more roundedcross-section and a conically-tapered tip 103 may be substituted.Moreover, the inner jaw member 102 of the cold jaw 42 is slightly longerthan the more blunt inner jaw member 62 of the first jaw 40 to furtherease dissection of tissue.

Attachment of the jaws 40, 42 to the distal end of the tissue weldershaft 36, and an exemplary mechanism for opening and closing the jawswill now be described. With reference to the exploded view of FIG. 4,and also to FIGS. 3 and 5, the pivot housing 66 of the first inner jawmember 62 comes together with a proximal pivot housing 104 of the secondinner jaw member 102, capturing the bushing 96 therebetween. The bushing96 includes oppositely directed shaft stubs 98 that fit within thealigned apertures formed in the pivot housings 66, 104, such as theaperture 67 seen in FIG. 6B. The bushing 96 includes features on oneside that mate with the particular shape of the pivot housing 66 andconductor wires 82, 84 arranged therein. In this regard, the bushing 96is fixed with respect to the pivot housing 66 of the first inner jawmember 62. The pivot housing 104 of the second inner jaw member 102, onthe other hand, includes a flat lower surface that slides across a flatupper surface of the bushing 96 when the housing pivots about the shaftstub 98. Consequently, the first inner jaw member 62 and second innerjaw member 102 are permitted to pivot with respect one another about theshaft stubs of the bushing 96.

The exploded view of FIG. 4 also shows the distal end of the flexibleshaft 36 which includes a stepped-down portion 110. The flexible shaft36 is hollow and receives a control rod 112 therethrough. A generallyY-shaped yolk 114 attaches to the distal end of control rod 112 througha resistance weld or similar expedient (not shown). Linear movement ofthe control rod 112 therefore also moves the yolk 114. The generallytubular shaft tip 54 fits over the stepped-down portion 110 and issecured thereto with a rivet 118.

With reference primarily to FIG. 4, but also FIGS. 2 and 3, the tubularshaft tip 54 includes a bifurcated distal end having a pair of arms 120defining side openings 122 therebetween. As will be explained, the pivothousings 66, 104 of the jaws extend between the arms 120 and the sideopenings 122 permit pivotal movement thereof. The assembly of the twopivot housings 66, 104 with the bushing 96 therebetween is sandwichedbetween a pair of small spacers 124 that have flat inner surfaces andpartial cylindrical outer surfaces. The spacers 124 include throughbores that align with the apertures 67 in the pivot housings and withthe inserted shaft stubs 98. The jaw assembly including spacers 124 thenfits between the bifurcated arms 120 and is secured therein with a rivet126 that passes through a pair of apertures 128 in the fingers, andthrough the aforementioned apertures. The jaws 40, 42 therefore pivotabout the shaft stubs 98.

Both of the pivot housings 66, 104 include the angled slots 68 that aregenerally aligned with elongated slots 130 formed in both of the arms120 of the shaft tip 54. As seen in the exploded view of FIG. 4, theangled slots 68 are oppositely oriented with respect to one another. Thecombined thickness of the assembled pivot housings 66, 104 fits betweenthe bifurcated fingers of the yolk 114 and a rivet 132 passes throughapertures in the distal ends of the yolk fingers and through the angledslots 68. In this way, linear movement of the yolk 114 translates intolinear movement of the rivet 132, which in turn opens and closes thejaws 40, 42 through a camming action in the angled slots 68. Theelongated slots 130 provide clearance for the rivet heads, ensure planaralignment of the rivets, and also facilitate assembly thereof. With theangled slots 68 oriented as shown, the jaws will be open when thecontrol rod 112 is displaced distally, while proximal movement of thecontrol rod closes the jaws.

Electricity can be delivered to the jaws 40, 42 through the conductorwires 82 and 84, best shown in FIG. 6B, or directly through the pivotingmechanism just described. For example, the control rod 112 may beelectrically conductive and provide current to the inner jaw members and62, 102 via the connecting the yolk, pins, and angled slots. The returncurrent path might be provided by a single conductive wire. Theillustrated embodiment utilizing conductor wires 82, 84 is preferredbecause it eliminates moving parts from the electrical conduction path.

Within the constraints of the small diameter design (less than 5 mm),the jaw movement mechanism should be relatively robust to be capable ofapplying a closing force of around 1-3 lb, preferably about 1 lb, and anopening force of around 1-3 lb. Further, the jaw opening distance at thedistal tips thereof is desirably about 8 mm. In addition to welding andcutting tissue, the jaws can also be used for blunt dissection becauseof the tapered and rounded outer shape of the jaws. This bluntdissection can also be enhanced by the relatively robust opening forceprovided by the jaws.

As will be apparent, the jaw opening and closing function can beachieved in many different ways. The present invention, in its broadinterpretation, is not particularly limited to any one type ofmechanism. For example, instead of both jaws pivoting about a commonaxis, a series of linkage members may be utilized with the jaws pivotingabout spaced axes. The form of jaw opening apparatus is preferablychosen to minimize cost and optimize transfer of linear force topivoting movement of the jaws. Optionally, the pivoting mechanism isconfigured such that the jaw-facing surfaces of the jaws remainparallel.

An exemplary control handle 38 seen in FIGS. 11A-11C and 12 contains amechanism for actuating the control rod 112 and opening and closing thejaws, in addition to several other desirable features. The controlhandle 38 is seen in elevation and two opposite partial sectional viewsin FIGS. 11A-11C. The control handle 38 includes an outer housing 140formed by the juxtaposition of two molded housing halves 140 a, 140 b.The outer housing 140 includes a plurality of walls and/or bulkheads 141that defined therebetween a series of internal housing cavities. Adistal through bore formed in the outer housing receives the flexibleshaft 36 leading to the distal jaws 40, 42. The aforementioned actuator44, in the illustrated example, is journalled to pivot about a pin 142fixed with respect to the housing, and includes a thumb pad 144 oppositethe pin 142. A narrow section of the actuator 44 travels within aproximal-distal slot 146 in the housing 140 such that the thumb pad 144provides a slider for the user. The actuator 44 is therefore constrainedto pivot in a hollow space between the two housing halves 140 a, 140 band the thumb pad 144 travels between opposite ends of the slot 146.Movement of the slider 144 in a distal direction (to the left in FIG.11A) closes the jaws, while movement of the slider in the proximaldirection (to the right in FIG. 11A) opens the jaws.

The exemplary control handle 38 includes circuitry for energizing theaforementioned heating elements at the distal end of the tool inaddition to the mechanism for opening and closing the jaws. Although theinvention is not limited to one particular switching arrangement, theexemplary embodiment includes a weld/cut switch that actuates both thewelding heating element and the cutting heating element simultaneously,and coincident with the jaw closed position. Moreover, the controlhandle 38 includes a governor for limiting the force that can be appliedby the jaws on tissue held therebetween.

With reference still to FIGS. 11A-11C, and in particular the explodedview of FIG. 12, the actuator 44 possesses an enlarged mid-section 150having a vertically elongated proximal-distal through bore 152 definedtherewithin. The through bore 152 receives therein a rod 154 having aproximal head 156 and a distal head 158. The proximal end of the rod 154extends through a force transfer block 160 and into a cavity to theproximal side of the actuator 44. The force transfer block 160translates in a proximal-distal direction between a pair of guide walls162 formed in the housing and includes a bore that slides over the rod154. A force-limiting spring 164 closely surrounds the rod and isconstrained between the proximal head 156 and the force transfer block160. The distal end of the rod 154 extends to the distal side of theactuator 44 such that the distal head 158 is captured within a forcecoupler 166. FIG. 12 illustrates best the internal contours of thegenerally box-shaped force coupler 166 which includes a large cavity, asmaller cavity in which the distal head 158 is received, and a pair ofslots on opposite ends thereof (elements not numbered for clarity). Oneside of the force coupler 166 is removed to facilitate assembly of thecooperating parts, as seen in FIG. 11C. Like the force transfer block160, the force coupler 166 translates in a proximal-distal directionbetween a pair of guide walls 174 formed in the housing.

With specific reference to FIG. 11B, a small tang 180 projects laterallyfrom the enlarged mid-section 150 of the actuator 44. The tang 180 ispositioned to engage and trip a weld/cut switch 182 mounted within thehousing 140. That is, the switch 182 is fixed with the respect to thehousing 140, while the tang 180 pivots with the actuator 44. When thethumb pad 144 translates in a proximal direction within the slot 146,the actuator 44 pivots in a clockwise direction until the tang 180actuates the lever of the weld/cut switch 182. An electrical wire 184extends into the proximal end of the handle 38 and provides power to theswitch 182. From there, an electrical lead 186 continues in the distaldirection and passes through the flexible shaft 36 to the heatingelements on the jaws at the distal end of the tool.

FIGS. 11B and 11C illustrate a cylindrical filter 190 captured betweenbulkheads 141 at the distal end of the housing 140. The generallytubular filter 190 is seen exploded in FIG. 12, and includes a steppedthrough bore 192 that receives, on either end, a pair of O-rings 194.The O-rings 194 each have an inner diameter that closely fits and sealsaround the flexible shaft 36. The shaft 36 extends into the distal endof the housing 140, through the filter 190, and terminates at a seal 196adjacent one of the bulkheads 141 of the housing. As shown in FIG. 11C,the control rod 112 continues through the seal 196 and into the forcecoupler 166. A collar 200 received in the large cavity of the forcecoupler 166 fastens to the proximal end of the control rod 112 with aset screw 202. In this manner, the proximal end of the control rod 112is constrained by the collar 200 within the force coupler 166.

In use, the operator slides the thumb pad 144 in a distal directionalong the slot 146 as seen by arrow 204 in FIG. 11C to pivot theactuator 44 and open the jaws of the tool. As the actuator 44 pivots,its angular movement is accommodated by the elongated through bore 152over the rod 154. A curved distal face of the enlarged mid-section 150eventually contacts the proximal end of the force coupler 166 and actsas a cam to urge it in a distal direction. Because the collar 200 isconstrained within the larger cavity of the force coupler 166, it alsotranslates in a distal direction which, in turn, pushes the control rod112 distally. In this embodiment, there is no clutch or force-limiterinterposed between the actuator 44 and distal movement of the controlrod 112 to open the jaws. Therefore, the extent that the jaws open islimited by the extent of travel of the thumb pad 144, or by the hingemechanism of the jaws themselves.

Conversely, the operator slides the thumb pad 144 in a proximaldirection along the slot 146 as seen by arrow 206 in FIG. 11B to pivotthe actuator 44 and close the jaws of the tool. A curved proximal faceof the enlarged mid-section 150 eventually contacts the distal end ofthe force transfer block 160 and acts as a cam to urge it in a proximaldirection. Because the force transfer block 160 is free to slide overthe rod 154, it moves in a proximal direction toward and compresses thespring 164. Compression of the force-limiting spring 164 applies aproximally-directed force to the proximal head 156 of the rod 154.Because the distal head 158 is constrained within the stepped cavity ofthe force coupler 166, which in turn is connected to the control rod112, the resistance to proximal displacement of the rod 154 is providedby any force resisting closure of the jaws (assuming minimal frictionalforces acting on the control rod 112). Prior to the jaws clamping anytissue, this resistance to proximal displacement of the rod 154 isminimal and proximal displacement of the force transfer block 160translates into equivalent displacement of the control rod 112. However,when the jaws finally close on tissue, the maximum closing force of thejaws is limited by the stiffness of the spring 164. Specifically, afterthe jaws close a constant force is applied to the tissue therebetweenbecause of the spring 164.

Through careful calibration of the force-limiting spring 164 inconjunction with the particular jaws on the tool, this closing force canbe limited to less than that which would unduly crush or otherwise causetrauma to the tissue within the jaws. Those of skill in the art willunderstand that it is the pressure applied to the tissue that must belimited, and that the pressure partly depends on the shape and size ofthe jaws, as well as the elastic constant of the spring 164. Desirably,the force imparted on tissue by the jaws is between about 1-3 lbs(0.45-1.36 kg), and preferably about 1 lb, as regulated by the spring164. This preferred range of force ensures the heating elementseffectively weld and sever tissue held within the facing surfaces of thejaws in a reasonably short amount time, preferably within 5 seconds orless. That is, applying a force of less than 1 lb to tissue tends todelay the cutting function, while application of a force greater than 3lbs tends to sever the tissue before an effective weld is formed. Again,this preferred force range and operation time to depend upon the sizeand shape of the jaws. However, given the constraints of endoscopictissue welding, in particular during vessel harvesting procedures, theseparameters are believed to encompass a wide range of suitable jaw types.

To better explained the desirable weld parameters of the tissue welder,the reader is directed back to FIGS. 8A-8H showing the inner jaw member62 of the hot jaw, and FIGS. 10A-10H showing the boot 52 a that coversthe inner jaw member 62. The inner jaw member 62 has the curved distalportion 64 extending from the proximal pivot housing 66, and a lengthfrom the circular pivot hole 67 to its distal tip of approximately 0.740inches (18.80 mm) As mentioned above, the inner jaw member 102 of thecold jaw 42 is slightly longer than the more blunt inner jaw member 62of the first jaw 40 to ease dissection of tissue, and preferably has alength of approximately 0.765 inches (19.43 mm). Desirably, the jawmember 62 is made of stainless steel, although other materials,thermally conductive or otherwise, may be utilized. The transversecross-sectional shape of the distal portion 64 is approximately squareadjacent the pivot housing 66, having a dimension on each side ofapproximately 0.060 inches (1.52 mm). The dimension of the tissue-facingside of the distal portion 64, seen in FIG. 8E, remains constant alongthe length of the jaw member 62, while the perpendicular dimension seenin FIGS. 8D and 8F gradually tapers smaller toward the distal tip to afinal dimension of about 0.031 inches (0.79 mm). The boot 52 a seen inFIGS. 10A-10H has an overall length sufficient to cover the curveddistal portion 64, and a transverse tissue-facing width of approximately0.082 inches (2.083 mm). The dimensional parameters of the boot 52 b ofthe cold jaw are equivalent, although the two boots perform differentfunctions and are thus configured differently.

The previously mentioned desirable clamping force of the jaws of between1-3 pounds can also be characterized in terms of pressure on the tissueto produce the most effective balance between severing and welding.Using the approximate dimensional values given above, the jaws desirablyexert a pressure on the tissue of between about 25-75 psi, averagedtransversely across the tissue-facing surfaces of the boots 52 a, 52 b.It should be understood that this range is an estimate based on thenon-uniform contours of the tissue-facing surfaces of the boots 52 a, 52b, and those of skill in the art will understand that structuralmodifications to the jaws may affect the preferred force and/or pressurerange. Moreover, the temperature to which the heating elements on thejaws rise also affects the preferred force applied, as well as theduration of the weld. Once again, a commonly accepted range oftemperatures at which human tissue may be welded is 50 to 90° C., whilesevering occurs at temperatures of 100° C. and above. Using theseguidelines, if the exemplary jaws apply a clamping force of between 1-3pounds on tissue and the welding and severing heating elements areenergized to these temperatures, a preferred duration of weld is between1-5 seconds. If the clamp duration is too short, the weld may not beeffective and the tissue is less likely to completely sever, while anexcessive duration above 5 seconds may tend to char tissue.

Still with reference to FIG. 11B, movement of the actuator 44 in thedirection of arrow 206 also displaces the tang 180 into engagement withthe weld/cut switch 182. Even if the intervening force-limiting spring164 limits further closure of the jaws, the actuator 44 can continuemovement until the switch 182 is tripped. The control handle 38 of thepresent invention further includes feedback to indicate to the useraurally and via tactile sensation through the thumb pad 144 when theswitch 182 has been tripped, both on and off. More particular, FIGS. 11Cand 12 illustrate a small protrusion 208 projecting laterally from theactuator 44. This protrusion pivots along with the actuator and engagesa small tooth 210 provided on a pivoting detent lever 212 (see FIG. 12).Although not shown in FIG. 11C, the detent 212 pivots about a pointfixed within the housing 140 and the tooth 210 is biased upward by adetent spring 214. The protrusion 208 cams past the tooth 210 whichdisplaces and provides both an audible and tactile click to the user atthe point that the switch 182 is tripped ON. Movement of the actuator 44in the opposite direction also causes the protrusion 208 to cam past thetooth 210, thus indicating when the switch 182 is turned OFF. In anexemplary procedure, the weld time is typically less than 5 seconds.

The exemplary control handle 38 illustrated in FIGS. 11A-11C and FIG. 12further includes a system for capturing smoke or particulate matter thatis generated by the distal jaws at the operating site within the tissuecavity. As mentioned above, various end effectors may be utilized withcertain aspects of the present invention, with resistance heatingelements being featured as the exemplary embodiment. Most of these endeffectors, including resistance heating elements, often cause asubstantial amount of smoke to be generated from the heated tissue.Often, the operation is performed using CO.sub.2 insufflation whichcreates a pressure gradient forcing gas in a proximal direction throughthe flexible shaft 36.

To control egress of this smoke through the flexible shaft 36, thecontrol handle 38 provides the aforementioned passive filter 190. Theflexible shaft 36 includes at least one gas escape port 220 at itsproximal end. This port 220 is positioned between the O-rings 194 andwithin the hollow interior of the filter 190. The hollow cavity withinthe filter 190 provides a venting chamber or space to receive the gassesfrom the port 220. In addition, the proximal end of the flexible shaft36 is capped by the seal 196 which conforms closely around the controlrod 112 and electrical lead 186. All of these seals force any gas (andsmoke or particulate matter) traveling proximally through the flexibleshaft 36 to exit through the gas escape port 220. Consequently, the gasis forced through the gas permeable material of the filter 190 whichtraps any smoke or particulate matter before it reaches the interior ofthe housing 140. From there, the now filtered gas, predominantlyCO.sub.2, passes through the various cavities within the housing 140 andexits through random fissures and openings therein.

Several alternative configurations for filtering smoke generated by thetissue welding procedure are seen in FIGS. 11D-11F. First of all, FIG.11D illustrates the exemplary control handle 38 having a small exhaustfan 222 mounted near its proximal end. The exhaust fan 222 helps pullgas passing through the elongated shaft 36 through the aforementionedpassive filter 190. In many instances means for gas insufflation isprovided in the overall system within which the tissue welders is used,which provides a positive pressure within the body cavity and forces gasproximally through the elongated shaft 36. However, in some procedureseither no insufflation is used or it does not generate sufficientpressure, in which case the auxiliary fan 222 helps pull the gas throughthe filter 190.

FIG. 11E illustrates the interior of an alternative control handle inwhich a cooling apparatus 224, such as a Peltier cooler, is mountedadjacent the gas escape ports 220 in the elongated shaft 36. The smokeemitted from the port 220 connect is on the cooling apparatus 224, whicheffectively passively filters the gas which is then permitted to exitfrom various openings in the handle.

Alternatively, FIG. 11 F illustrates a further alternative controlhandle in which a plurality of louvers or fins 226 are arranged adjacentthe gas escape ports 220. The fins 226 diffuse and condense the smoketraveling proximally through the elongated shaft 36, and thus act as apassive filter. The gas is then permitted to exit from various openingsin the handle. Because the surface area through which the smoke exhaustsis expanded, the density of that smoke is decreased making it lessnoticeable as it exits the handle. In the illustrated embodiment, thefins 226 are configured as a series of concentric annular elements, butother arrangements are possible.

FIGS. 13A-13C illustrate an alternative control handle 38′ similar tothat described above but including a separate electrical circuit for afasciotomy cutter provided on a distal tool. As mentioned above,fasciotomy comprises an incision through fascia (e.g., bands or filletsof fibrous tissue that separate different layers of tissue). The tissuewelding/cutting jaws may also be adapted to include such a fasciotomycutter which enables the tool to be moved linearly through to cut tissuewithout opening and closing the jaws. The fasciotomy cutter may be aseparate heating element provided on the forward end of one of the jaws,or within the jaws. Some of the elements illustrated for the alternativecontrol handle 38′ are common to the control handle 30 described abovewith respect to FIGS. 11-12, and therefore will be given the sameelement number with a prime “′” designation.

As seen in FIGS. 13B-13C, the flexible shaft 36′ from the distal toolenters the molded housing 140′, and a control rod 112′ projectstherefrom into a cavity formed within the housing and is fixed to anenlarged collar 230. Although not shown, a shaft member 232 fastened tothe collar 230 extends in a proximal direction through a fasciotomyspring 234, and through an actuator 44′ to terminate at a proximal head236. The actuator 44′ is much like the actuator 44 described above, witha body that pivots about a pin 238 and has an elongated through bore forpassage of the shaft 232. The distal end of the shaft 232 having thecollar 230 thereon translates within a proximal-distal cavity 240, whilethe proximal end of the shaft having a proximal head 236 translateswithin a proximal-distal cavity 242. Because the control rod 112′ isrigidly fastened to the collar 230 which in turn is fastened to theshaft 232, movement of the shaft produces identical movement of thecontrol rod.

With particular reference to FIG. 13C, an annular cam follower 244surrounds the shaft 232 between the actuator 44′ and the fasciotomyspring 234. The cam follower 244 includes a short slot (not numbered)within which extends a small pin 246 projecting laterally from the shaft232. In the position illustrated, the actuator 44′ is in a neutralposition not in contact with the cam follower 244, which in turn istherefore biased in a proximal direction by the fasciotomy spring 234 asfar as the pin 246 and slot permit. A second cam follower 250 surroundsthe shaft 232 between the actuator 44′ and the fasciotomy spring 234. Aforce-limiting spring 252 is concentrically constrained around the shaft232 between the proximal head 236 and the second cam follower 250. Asnoted, the actuator 44′ is in the neutral position out of contact withthe second cam follower 250, and thus the force-limiting spring 252remains uncompressed.

A user displaces the thumb pad of the actuator 44′ in a proximaldirection as indicated by arrow 260 in FIG. 13B, which pivots theactuator 44′ and urges the cam follower 244 in a proximal direction.Compression of the fasciotomy spring 234 causes proportionaldisplacement of the collar 230 and control rod 112′, therefore openingthe jaws of the tool. At a certain distance of travel, the collar 230reaches the end of the cavity 240 and further movement of the controlrod 112′ is impeded, corresponding to the maximum opening distance ofthe jaws. However, because the cam follower 244 includes the linear slotin which the pin 246 travels, the actuator 44′ can continue its movementforcing the cam follower 244 proximally against the compressive force ofthe spring 234. The user experiences a resistance to movement of theactuator 44′ during this stage, which is an indication that thefasciotomy heater is activated. In particular, a tang 262 (FIG. 13C) onthe actuator 44′ eventually engages a fasciotomy switch 264 at the pointthat the fasciotomy spring 234 is being compressed. Although thecircuitry is not shown, the switch 264 is supplied with current and whenswitched ON provides current to leads extending through the flexibleshaft 36′ to the distal end of tool and fasciotomy heating element.

Conversely, the user displaces the actuator 44′ in a proximal directionas indicated by arrow 270 in FIG. 13C to close the jaws. A proximal faceof the actuator 44′ cams against the follower 250, which in turn actsagainst the force-limiting spring 252. As in the earlier embodiment, aminimal reaction force exists prior to the jaws closing and thusmovement of the actuator 44′ causes proportional movement of the controlrod 112′. At the point that the jaws close over tissue, theforce-limiting spring 252 determines the amount of pressure that may beapplied to the tissue before further movement of the actuator 44′ merelycompresses the spring without moving the control rod 112′. Near thelimit of travel of the actuator 44′ in the direction of arrow 270, thetang 262 engages a weld/cut switch 272 mounted within the housing 140′,thus actuating the welding and cutting heating elements at the distalend of the tool. The alternative control handle 38′ further includes adetent 274 that acts in the same manner as the detent 212 describedabove and indicates to the user when the weld/cut function is ON andOFF.

FIGS. 14A-14C illustrate a preferred linkage 300 between a control rodand the jaws for opening and closing the jaws. In the jaw openingmechanisms of the prior art, certain disadvantages were recognized thatincrease the overall size of the jaw assembly, increase the cost ofconstruction, exposed electrical connections to wear, or sacrificedmechanical and electrical consistency by including excess sources offriction, and sacrificed electrical consistency by relying on movingmechanical connections for electrical continuity, for example. Theexemplary linkage 300 and the associated “hard-wired” electricalconnection reduces the overall size of the jaws assembly, reduces thenumber of components and associated cost and complexity, improves therobustness of the mechanics, and improves the mechanical and electricalreliability (i.e., consistency) of the device.

A pair of jaws 302, 304 are shown open in FIGS. 14A and 14B. Each jawincludes a through bore that is journalled about a shaft 306, such asthe shaft stub 98 as seen in FIG. 5B. In this manner, proximal housings308, 310 of the respective jaws pivot with respect to one another. Anangled slot 312, 314 is provided in each pivot housings 308, 310. Anactuating pin 316 extends into both of the angled slot 312, 314 and isconnected to a proximal control rod (not shown). FIG. 14B illustratesthe distal end of a tool shaft 320 that encompasses the pivot housings308, 310. The tool shaft 320 includes a linear slot 322 within which theactuating pin 316 translates. The distal end of the tool shaft 320 shownis analogous to the shaft tip 54 seen in FIGS. 2 and 4.

FIG. 14C shows movement of the actuating pin 316 to the left whichcauses the jaws 302, 304 to close. That is, the pin 316 cams the angledslots 312, 314 such that their proximal ends come together as seen. Ofcourse, the reverse movement of the actuating pin 316 causes the jaws toopen again. Because of the simplicity of the mechanism, the overall sizeof the jaw assembly can be reduced so that it fits through a 5 mm insidediameter tube. Furthermore, the reduction in the number of parts obtainsan equivalent reduced manufacturing time and complexity, for a lowermanufacturing cost. The moving parts consist of the actuating pin 316translating within the three slots, and the two jaws which pivot withrespect one another. This reduces the sources of friction and thusimproves mechanical reliability. Finally, the angle of the slots 312,314 may be adjusted to change the actuation force required to open andclose the jaws. That is, a shallower angle would necessitate a lowerforce from the control rod to actuate the jaws. The trade-off, of courseis that the opening distance of the jaws is concurrently reduced.

Clearly, the dual- or tri-heating element function can be achieved inmany different ways. The present invention broadly includes a heatingelement for cutting tissue and a heating element for welding tissue, andis not particularly limited to any one type of either apparatus.Examples include, but are not limited to two, three, or more heatingelements, cutting and welding heating elements separately activated orconnected in series or parallel, or both, heating elements on one orboth jaws, etc. The form of the multiple heating elements is preferablychosen so that they are relatively close together and one reliably cutsand the other reliably welds a variety of tissue. Optionally, themultiple heating elements are configured such that they operatesubstantially simultaneously and ensure good hemostasis of the weldedtissue. The power applied and shape of the heating elements are chosento ensure that inadvertent tissue charring or other such damage does notoccur inadvertently during normal operation of the device. The primaryclinical benefits of the heating elements of the present inventioninclude but are not limited to balance of power outputs from cutter andwelder(s) for consistently strong welds, as well as thermal efficiencyfor faster weld times.

It should be understood that the force-limiting function of the springwithin the control handle can be achieved in many different ways. Thepresent invention, in its broad interpretation, is not particularlylimited to any one type of mechanism for limiting the closing force ofthe jaws, but is characterized by a force-limiting interface between thecontrol actuator and the elongated jaws for limiting the magnitude ofclosing force of the jaws. Examples include, but are not limited to theaforementioned spring provided within the control handle, a similarspring provided distal to the control handle, a pressure transducer onthe jaws which provides feedback to the user or other device forlimiting the force applied by the jaws, compliant jaws, etc. The form ofthe force-limiting apparatus is preferably chosen to limit the pressureapplied to tissue by the particular jaws. Optionally, the force-limitingapparatus is configured simply in a cost-effective manner. Theforce-limiting apparatus is chosen to ensure that crushing of tissuedoes not occur inadvertently during normal operation of the device.

While the tissue welding system described thus far is believed to beparticularly effective, the present invention also provides a number ofalternative jaw and heating elements which are each believed to bepatentable in its own right. A number of these alternatives will now bedescribed briefly with reference to FIGS. 15-37. It should be understoodby the reader that generally, any of these jaw or heating elementconfigurations can be coupled with any of the aforementioned controlhandle/shaft embodiments. For example, if a particular jaw includes afasciotomy cutter in addition to a tissue cutter and a tissue welder, itmay be used with the control handle 38′ of FIGS. 13A-13C, but alsoaspects of the control handle 38 of FIGS. 11-12 may be substituted.

Prior to a discussion of the multiple alternative embodiments, it isimportant to understand the basic structure of the exemplary embodimentdescribed above. FIG. 15 illustrates in cross-section a first jaw 330spaced from a second jaw 332. Both jaws include an inner jaw 334surrounded by a boot 336. As will be understood shortly, the materialsof the inner jaws 334 and boots 336 may be specifically designed tocontrol the heat concentration/dissipation within the jaws 330, 332. Inthe exemplary embodiment, however, the inner jaws 334 are made ofstainless steel while the boots 336 are silicone. The lower jaw 330 isthe “hot” jaw, and includes multiple heating elements outside the boot336. Specifically, a first heating element 338 extends along the inneror jaw-facing surface 339 of the first jaw 330, and comprises at leasttwo welding members, one each on either side of a centrally disposedsecond heating element 340. Both the first and second heating element338, 340 are positioned outside the boot 336, which is shown having aplanar jaw-facing surface 339 and a rounded outer surface (notnumbered). The first heating element 338 is supplied with power and actsas a welding heater, while the second heating element 340 reaches ahigher temperature and, also because of its smaller cross-section, actsas a cutting heater. As described above, in some embodiments, thewelding members of the first heating element 338 are connectedelectrically in series with the single second heating element 340, butin parallel with each other. The lower current through the parallelwelding members results in less heat generation and lower tissuetemperatures than the cutting heater, facilitating tissue welding.

FIGS. 16A-16B show a slight variation on a first jaw 330′ wherein theouter boot 336′ defines a centrally located and longitudinally directedchannel or depression 342 within which the second heating element 340′resides. A comparison of the cross-sections of FIGS. 15 and 16B showsthat the second heating element 340′ is somewhat larger in diameter thanthe earlier heating element 340, which size difference is accommodatedby the depression 342. In this way, various configurations of cuttingheaters may be utilized without unduly increasing the elevation relativeto the first heating elements 338.

FIG. 17 illustrates another possible variation on the hot jaw 330″ inwhich only one heating element 344 is provided. Instead of a secondheating element, the first heating element 344 is placed on a conductiveplate 346, preferably within a centrally located channel or depression348. Although not shown, the conductive plate 346 is desirablyelectrically insulated from the heating element 344. When the heatingelement 344 is activated, it generates sufficient heat to cut throughtissue while the conductive plate 346 absorbs some of the heat tofunction as tissue welding surfaces. The conductive plate 346 may bemade of copper, aluminum, or ceramics high in thermal conductivity, suchas Alumina. An insulating layer between the heater 344 and depression348 may be provided by a layer of ceramic, Teflon, polyimide, or othersuch material capable of withstanding high temperatures. With thepassively heated weld plate 346, this design only requires a singleelectrical circuit looped through the heating element 344.

The use of a heat sink on both sides of the tissue welder in jaws tolimit thermal spreading is also contemplated by the present invention. Aheat sinking wire or jaw insert may be provided on both sides of the hotwire, such as in the position of the heating elements 338 in FIG. 15.Alternatively, the heat sink may be provided on the jaw opposite the hotwire. In either situation, heat flux transfer lines will travel from thehot wire to the heat sink, thus limiting thermal spread and volume oftissue heated. To further enhance this focused heating, thermalinsulation may be provided on the outboard faces of the heat sinks orjaws to retain the applied heat inside the jaws.

In each of the designs shown in FIGS. 15-17, the temperature profileachieved is a high temperature along the jaw midline for cutting, with alower temperature on both sides for welding without cutting. Thisresults in the formation of a wider, more consistent weld band than witha single heater over the midline of the boot, as present in prior artdevices. In particular, when used to cut and weld vessels, the resultingwider weld band is stronger and more consistently prevents subsequentleaks.

Now with reference to FIGS. 18A-18C, an alternative jaw configuration isshown that again includes multiple heating elements, but instead of allbeing on one of the jaws they are distributed on both jaws. Moreparticularly, a first jaw 350 possesses a first heating element 352 inthe shape of a relatively wide plate on the jaw-facing surface of theboot. A second jaw 354 includes a second heating element 356 comprisinga relatively narrow wire, again placed on the jaw-facing surface of theboot. The second heating element 356 is desirably positioned at theapproximate lateral midline of the second jaw 354. Because the heatingelements 352, 356 are on different jaws, they may conveniently besupplied with power through separate circuits. Through choice ofmaterials, current supplied, and size difference between the two heatingelements, the first heating element 352 welds tissue while the secondheating element 356 reaches a higher temperature and cuts tissue. FIGS.18B and 18C schematically illustrates the temperature profiles of thejaw-facing surfaces of the two jaws 350, 354 when the respective heatingelements are activated.

Because the heating elements 352, 356 of FIG. 18A may be energizedthrough separate circuits, they may be activated at different times. Oneembodiment of the present invention is a two-stage heating process inwhich current runs through the first heating element 352 to form a weldband in the tissue or vessel. Subsequently, current passes through thesecond heating element 356 to generate a localized hot zone and cut thetissue or vessel in the middle of the weld band. As mentioned above, thetotal weld time is desirably less than 5 seconds, and therefore onemethod contemplated is to energize the first heating element 352 forbetween 3-5 seconds, switch the first heating element off, energize thesecond heating element 356 until the tissue or vessel severs, and thenswitch the second heating element off.

Inner Jaws of Low Thermal Conductivity

Certain designs of tissue welder jaws of the prior art included astainless steel inner jaw covered with a silicone boot or jacket. Aheating element outside of the silicone boot was directly attached tothe stainless steel inner jaw on its underside (i.e., on the side facingaway from the other jaw), and the inner jaw therefore served as a returnpath for the electrical current through the heating element. However,with this configuration the stainless steel inner jaw retains asignificant amount of heat energy during the thermal welding process,thereby adversely affecting the consistency and efficiency of thethermal tissue-welding system. Furthermore, the electrical contactbetween the heating element and stainless steel created a direct heatconduction flow path. To address this thermal inefficiency, the presentinvention contemplates limiting the amount of heat energy that istransferred to the inner jaws either at the attachment of the heatingelement to the jaw and/or along the length of the heating element, andalso by material choice.

For example, the inner jaws may be fabricated of a thermally-insulatingmaterial having significantly lower thermal conductivity than stainlesssteel (17.9 Watts per meter-Kelvin: W/m-K). More specifically, the innerjaws are desirably fabricated of a material having a thermalconductivity of less than about 5.0 W/m-K. A number of ceramics havingthe desirable low thermal conductivity are suitable, including alumina,machinable glass ceramic (e.g., MACOR), zirconia, yttria, and partiallystabilized zirconia (e.g., YTZP). MACOR has a thermal conductivity ofabout 1.6 W/m-K, zirconia is 1.675 W/m-K, and YTZP is 2.2 W/m-K. Theinner jaws may be formed completely of one of these low thermalconductivity materials, or a conventional stainless steel inner jaw maybe completely or partly coated with the material, which impedesconductive thermal transfer to the stainless steel. The material may befabricated by machining (e.g., MACOR) or ceramic injection molding(e.g., zirconium and YTZP). In addition, the electric circuit for theheating element may be formed as conductive traces on the ceramicmaterial, as opposed to using the inner jaw as the return current path,even if an inner jaw is still used. Through the use of these traces 366,370, and by choosing a relatively electrically insulating inner jaw 362,current does not pass through the inner jaw.

For example, FIGS. 19A-19E illustrate an exemplary jaw 360 including aninner jaw 362 of a low thermal conductivity material (<5.0 W/m-K) havinga sloped distal end. A heating element 364 is seen on an inside face ofthe inner jaw extending longitudinally along a main portion and thensloping downward along with the inner jaw. The heating element 364 formsa part of the circuit completed by a number of copper traces extendingalong the inner jaw 362. More specifically, a first trace 366 extendsalong one lateral side of the jaw 360 and connects with the heatingelement 364 near the distal tip thereof, as seen at 368. The returncurrent from the proximal end of the heating element 364 passes througha second trace 370 that is connected to a ring-shaped conductor 372 thatmay be used to surround a pivot shaft. Although not shown, electricalwires along a flexible delivery shaft of the tissue welder complete thecircuit.

FIGS. 19C and 19D illustrate two alternative cross-sections for amidportion of the jaw 360. In FIG. 19C, the inner jaw 362 is generallysemi-cylindrical in shape with a flat clamping surface 380 interruptedby a centrally located semi-cylindrical rail 382. The relatively thinheating element 364 conforms in a semi-tubular shape around the rail382. In this configuration, the apex of the heating element 364 impartsthe greatest pressure to tissue clamped between the jaw 360 and theopposing jaw (not shown), and thus performs the cutting function. Thelateral portions of the heating element 364 to both sides of the apexare in relatively lesser degrees of contact/pressure with the tissue,but are still heated, and effectively weld the tissue on both sides ofthe cut line. FIG. 19D illustrates an alternative shape for the heatingelement 364 which exhibits both an upstanding narrow central rail 390and a pair of relatively flat shoulders 392 adjacent the rail. Theupstanding rail 390 performs the cutting action, while the flatshoulders 392 weld the adjacent tissue.

The jaw 360 of FIGS. 19A-19E further includes a distal fasciotomysection 394 at the point at which the inner jaw 362 slopes. FIG. 19Adepicts a narrowing of the heating element 364 in this section, and FIG.19E shows the cross-section of the inner jaw 362 which includes arelatively pronounced rib 396 around which the heating element conforms.Because of this pronounced shape of the heating element 364 in thesloped section 394, forward movement of the jaws through tissue with theelement 364 activated easily performs a cutting action. The jaws can beopen or closed. In this embodiment, the fasciotomy heater is merely anextension of the joint cutting and welding heater, and all of theseportions of the heating element 364 are energized simultaneously. As wasexplained above, however, a separate fasciotomy cutter having the shapeand position as shown may also be provided so that it can be turned offwhen the tissue severing and welding operation is underway, and viceversa.

As mentioned above, the present invention provides a number of solutionsto reduce heat loss to the jaws and thus make them more efficient fortissue welding, including modifying the arrangement of the heatingelement, inner jaw, and silicone boot. FIG. 20 illustrates aconventional longitudinal cross-section of a “hot” jaw 400 having aninner jaw 402 surrounded by a silicone boot 404. A heating element 406is shown extending along an upper or clamping face of the jaw 400. Theheating element 406 extends around a distal end of the jaw 400 at 408,passes through an aperture formed in the boot 404, and electricallycommunicates with the inner jaw 402 at a solder point or resistance weld410, for example. The inner jaw 402 is made of stainless steel andprovides a return current path for the electricity passing through theheating element 406. With this configuration, a significant amount ofheat is stored by the inner jaw 402, with heat loss exacerbated by thephysical connection between the heating element and the inner jaw.

FIGS. 21A-21E illustrate a number of alternative jaw cross-sections thatreduce the amount of heat lost to the inner jaw, typically stainlesssteel. It should be understood that certain of these variations may notbe mutually exclusive, and can be combined into numerous permutationswithin the scope of the present invention.

In FIG. 21A, a “hot” jaw 420 is constructed much like the jaw 400 of theprior art with an inner jaw 422 of stainless steel, a silicone boot 424,and a heating element 426 that extends along the jaw and wraps aroundthe distal end to be resistance welded to the underside of the innerjaw. Again, the inner jaw 422 provides a return current path. To reducethe amount of heat lost to the inner jaw 422, the inner jaw has acoating 428 on its upper surface of a thermally-insulating materialhaving significantly lower thermal conductivity than stainless steel(17.9 Watts per meter-Kelvin: W/m-K), and preferably less than about 5.0W/m-K. For example, a ceramic zirconia-based coating having a thermalconductivity of about 1.675 W/m-K may be used. In this way, a thermallyinsulating barrier extends along the majority of the heat generatingportion of the heating element 426, thus impeding conductive heat flowto the inner jaw 422.

An alternative jaw 430 in FIG. 21B comprises an inner stainless steeljaw 432, a silicone boot 434 therearound, and a heating element 436 onits upper surface. Instead of using the inner jaw 432 as a returncurrent path, the heating element 436 wraps around the distal end of thejaw 430 and connects to a conductive wire 438, for example, whichphysically decouples the heating element 436 from the inner jaw 432. Theheating element 436 and wire 438 may be connected through a solder pointor other similar expedient. In an exemplary combination, the jaw 430shown in FIG. 21B may be supplemented by a ceramic coating such as thatshown at 428 in FIG. 21A to further reduce heat loss to the inner jaw432.

FIGS. 21C and 21D illustrate, respectively, similar jaws 440, 442 inwhich the inner jaws 444 are again not used as a current return path.The inner jaws 444 could be stainless steel, or a ceramic to reduce thepotential for heat loss thereto. The heating elements 446 both connectto wires 448 extending proximally through a space between the inner jaws444 and the surrounding boots 450. If the jaws 444 are stainless steel,then the wires 448 are insulated such that there is no electricalcontact therebetween. The difference between the jaws 440, 442 and thejaw 430 in FIG. 21B is that the wires 448 are concealed underneath theboot 450, as opposed to extending along the outside of the boot. To helpprevent tearing of the typically silicone boot 450, the heating elements446 extends into apertures that are not at the distal tip of the jaws440, 442. In FIG. 21C, the aperture is on the underside of the jaw 440,while in FIG. 21D the aperture is on the upper face of the jaw 442.

FIG. 21E illustrates a still further alternative jaw 454 that improvesover the prior art jaw designs by improving the rate of transfer of heatto the tissue from a heating element 456. Specifically, a coil spring458 is placed around the heating element 456 to help transfer heat morequickly to the tissue. Desirably, a very close-loop coil should be usedto prevent tissue buildup between cycles, and may be coated with anonstick media such as silicone to further help prevent tissue buildup.The spring 458 may be attached mechanically to the heating element 456such as with a ceramic material to prevent an electrical short-circuit.Further, the coil spring 458 desirably has approximately the sameelectrical resistance as the material of the heating element 456 so thatthe magnitude of power applied to the heating element need not besignificantly increased.

FIGS. 22A and 22B schematically illustrate two different sets of jaws460 having tissue clamping plates 462 thereon and either a single ordual, heating elements 464 electrically connected in parallel. FIGS. 22Aand 22B represent jaw configurations for a variety of differentmaterials and combinations, including heaters on one or both sides ofthe tissue and various materials used to clamp the tissue. For example,ceramic jaws 460 (e.g., Macor) may be used.

FIG. 23 illustrates another configuration wherein a single heater 470 isprovided on a lower jaw 472 while an upper jaw 474 has no heater, butboth include surrounding boots that help promote tissue release. Theupper jaw 474 is reversed such that the rounded surface 476 of the bootfaces the first jaw 472. This configuration may help promote tissuerelease from the boots.

Jaws With Passive Welding Segments

In most of the earlier-described embodiments, multiple heaters are used,with at least one that performs a cutting function and one that performsa welding function. The present invention also contemplates providing asingle heating element that performs both these functions, such as theembodiment seen in FIG. 19D. In addition, the present inventionencompasses jaws that include a single heating element for cuttingtissue in conjunction with a passive region surrounding the heatingelement that coincidentally also heats up and provides a tissue weldingarea. Essentially, these designs are intended to better control heatapplication and temperature distribution within the tissue duringthermal welding in order to achieve a wider weld band, a more consistentweld bandwidth, a thinner cut band with respect to the weld band, and/ordecreased or more consistent weld times.

FIGS. 24A-24C illustrate three different alternative embodiments oftissue welding jaws that incorporate a material within the boots andadjacent to the heating element that provide a “hot zone” for welding.More specifically, each of these jaw designs includes a hot jaw 480shown spaced from a cold jaw 482. Both the hot jaw 480 and the cold jaw42 include inner jaws surrounded by boots, as has been described.Directly, the cross-sectional shape of the jaws 480, 482 issemi-cylindrical with a flat jaw-facing surface and a rounded outersurface. Each of the hot jaws 480 is provided with a heating element 484centrally located and longitudinally disposed on the flat jaw-facingsurface of each boot.

In FIG. 24A, a strip of thermally conductive material 486 extendsunderneath the heating element 484 and forms a continuation of the boot(i.e., has a similar thickness as the boot). In FIG. 24B, a strip ofthermally conductive material 488 likewise runs co-extensively under theheating element 484. In contrast to the strip 486 in FIG. 24A, the strip488 of FIG. 24B is somewhat thinner and resides in an inset of the boot.Finally, the hot jaw 480 of FIG. 24C includes a strip of thermallyconductive material 490 that is embedded within the boot, as can beachieved by various molding techniques. Each of these strips 486, 488,490 absorbs some of the heat generated by the heating element 484 andmore quickly spreads heat to tissue within a “hot zone” defined betweenthe jaws and within the width of the respective strips. The strips 486,488, 490 may be made of a suitable metal such as, for example, stainlesssteel. This hot zone forms a seal in the tissue and eventually theheating element 484 reaches a temperature that severs the tissue withinthe hot zone. The rate of temperature increase and material selected aresuch that the tissue is welded across the width of each of these strips486, 488, 490 prior to the tissue being severed by the heating element484. In a variation on these embodiments, both boots on the hot jaw 480and cold jaw 482 may be provided with the strips of thermally conductivematerial to further enhance heating of the tissue within the hot zone.

Multiple Heating Elements and Staged Heating

FIG. 25 illustrates a still further alternative embodiment of thepresent invention in which multiple heating elements are used. A hot jaw492 is shown spaced from a cold jaw 494. The hot jaw 492 includes anelectrically conductive first heating element 495 having a semi-annularconfiguration and a rod-like second heating element 496. A semi-annularlayer of insulation 497 is interposed between the first and secondheating elements which are concentrically arranged. After tissue hasbeen clamped between the jaws 492, 494, the first heating element 495 isenergized such that its temperature reaches a weld zone and forms a weldband in the tissue. After a predetermined amount of time, current is runthrough the second heating element 496 which heats up to a highertemperature through either higher current or higher resistance, whereinthe tissue is severed in the middle of the weld band.

In a slight variation on previously described embodiments, the secondheating element 496 may have a wire diameter that increases from aproximal end of the jaw to the distal end. In this way, a constanttemperature along the jaw is maintained because more heat is lost fromthe distal end. Those of skill in the art will understand that there areother ways to ensure a constant temperature along the length of the jaw,such as by varying the materials and/or resistance of the heatingelement 496.

Fasciotomy Cutters Incorporated into Tissue Welding Jaws

In addition to being able to weld and sever tissue, tissue welders ofthe present invention may also be capable of performing fasciotomy, oran incision through facia or layers of tissue. This is particularlyadvantageous when the tissue welder is used in an vessel harvestingoperation in which various layers of facia surround the target vessel. Atissue welder that incorporates a fasciotomy cutter allows for rapid,continuous transection of tissue and vessels, typically undervisualization with an endoscope.

FIGS. 26A and 26B are schematic views of an exemplary tissue welderhaving a fasciotomy cutter. A hot jaw 500 and a cold jaw 502 areschematically illustrated on the right side, open in FIG. 26A and closedin FIG. 26B a heating element 504 is provided on the jaw-facing surfaceof the hot jaw 500 and may take form of any of the various embodimentsdescribed herein. In addition, a cutting element 506 is located at theapex of the jaws 500, 502, approximately perpendicular to the heatingelement 504. Both the heating element 504 and cutting element 506 areconnected to a power supply as shown and wired in parallel to aninterlock switch 508. When the jaws 500, 502 are open and the device isactivated by the user, current is routed through the cutting element506. Conversely, when the jaws are closed and the device is activated bythe user, current is routed to the welding element 504. The user couldhave control of both the activation switch and the interlock switch 508,or the interlock switch could be mechanically linked to the position ofthe jaws.

A variation on the fasciotomy cutter shown in FIGS. 26A-26B is to placea fasciotomy heater wire 510 on the distal end of one of the jaws asseen in FIG. 27. A similar arrangement was shown previously in FIG. 19B,though the fasciotomy wire 510 may form a series extension of thewelding element, or may be a separately activated heating element as inFIGS. 26A-26B. The distal tips of the upper and lower jaws in FIG. 27are angled in a proximal direction toward one another such that when thejaws are closed they guide the facia toward the heater wire 510.

FIG. 28 illustrates a still further fasciotomy cutter 520 on a pair oftissue welding jaws. In this case the cutter 520 comprises a knife edgeor blade longitudinally disposed on a midline of an outer surface of oneof the jaws. The blade 520 could be retractable such that the user onlyextends it when fasciotomy is desired. Further, the knife blade 520could be resistively heated such that it more easily slices throughfacia.

FIG. 28 illustrates a still further alternative aspect of the presentinvention wherein indicator markings 522 are placed on the side of oneor both of the jaws. The indicator markings 522 could be placed inmillimeters increments so that adjustments in power setting and weldtime can be made to account for varying vessel sizes. Preferably, acentering marker larger than the others is provided as shown such thatthe user can optimally center a vessel within the jaws.

Control of Temperature Increase

Current tissue welders utilize a constant DC current to drive theheating elements. Therefore, the power delivered to the heater isconstant (P=I²·R). A typical graph of the temperature of the heatingelement over time is shown in FIG. 29. After switching current on, thereis a preheat phase 530 in which time the heating element's temperatureincreases to the weld temperature. After that, there is a period of time532 when the tissue is sealed or welded. Finally, the heating elementtemperature increases further at 534 to cut the tissue. The timenecessary for the preheat stage 530 is essentially wasted, and slowsdown the overall operation when a number of welding steps are required.Increasing the current during the preheat stage 530 would shorten thistime, but might cause the temperature to overshoot the weld temperatureand perhaps form charring. Such overshoot might also cause the tissue tobe severed before being probably sealed.

One solution to this issue is to place a Polymer Positive TemperatureCoefficient (PPTC) device, which has a resistance that varies as in thecurve of FIG. 30, in series electrically with the heating element. Thesedevices exhibit a rapid increase in their resistance at their triptemperature. FIGS. 31A and 31B schematically illustrate a circuit havinga heating element 540 that represents any of the heating elementsdescribed herein. The circuit loops through the heater 540 and through aPPTC device 542 electrically connected in series therewith. Through thechoice of the PPTC material, the temperature at which the materialbecomes highly resistive equals the weld temperature. This allows thematerial to be used as a temperature control switch that regulates thetemperature of the heating element 540 by acting as a closed switchbelow the weld temperature, and as an open switch above the weldtemperature. Therefore, a higher current can be used to raise thetemperature of the heating element 540 more rapidly and reduce thepreheat time, but the PPTC element 542 prevents overshoot of thetemperature.

An alternative configuration of the use of PPTC material is seen inFIGS. 32A and 32B. In this version, a rod-like PPTC element 550 residesconcentrically within an outer tubular heating element 552 with atubular layer of electrical insulation 554 therebetween. Thisconfiguration of heating element 552 more closely resembles theearlier-illustrated tubular embodiments. The circuit passes through theouter heating element 552 and back through the centrally located PPTCelement 550. The insulation around the rod-like PPTC element 550 musthave a high resistivity to block DC current, but should be thin enoughto allow good heat transfer between the heater and the PPTC material. Inthis way, even or monolithic heating of the entire assembly is notunduly hindered.

In an alternative embodiment not specifically illustrated, any of theheating elements disclosed herein may be constructed of a PositiveTemperature Coefficient of Resistance (PTCR) material whose electricalresistance is not constant over a predetermined temperature rangeincluding the weld temperature, and typically exhibits a generallylinear relationship between electrical resistance and temperature (i.e.,higher resistance at higher temperatures). This allows for rapid initialrate of temperature increase, so that the heating element rapidlyapproaches the desired welding temperature. As the temperatureapproaches the weld temperature, the rate of increase slows down due tothe increased resistance of the PTCR element. This prevents the heatingelement from overshooting the desired temperature, and potentiallyprematurely transecting the tissue or vessel. Advantageously, the rapidinitial rate of temperature increase reduces the overall welding time.Instead of using PTCR as the heating element itself, an alternative isto place a PTCR element in series with the heating element, much like isshown in FIGS. 31 and 32 with respect to PPTC elements. As the PTCRelement is heated from the applied current, the total resistance of thecircuit increases resulting in less current through the heating elementand a similar temperature governing effect.

In prior art systems, the constant current delivered to the heater isset by using a control knob on the power supply. If the current is sethigh to rapidly increase the heater temperature, an inadequate weld mayresult. Conversely, if the current is set low, the weld times may be toolong. Furthermore, a current setting that is optimal for a given sizevessel may be inadequate for different vessel diameter.

One methodology for closely controlling the temperature of the heatingelement in any of the embodiments described above is to utilizetemperature sensing and feedback through a processor, as seen in FIGS.33A-33C More specifically, FIG. 33A illustrates a system which activelymonitors and controls the temperature of tissue within the jaws of thethermal tissue welding device. The system comprises a controllable DCpower supply 560, tissue welding jaws with temperature sensing capacity562, a processor having a data acquisition system 564, and a controlalgorithm 566 such as within a laptop interfaced with the processor. Thepower supply 560 desirably provides 100 W DC, and its output may bevaried from 0-24 VDC using a pulse width modulated (PWM) input controlsignal (FIG. 33B), where the duty cycle of the PWM input signaldetermines the level of the DC voltage output (i.e., V_(out)=24 (1−dutycycle)). Input for the power supply 560 is received from the dataacquisition system 564, and the power supply output is connected to theheater of the tissue welding device.

In an exemplary configuration as seen in FIG. 33C, one of the tissuewelding jaws has a thermocouple 570 placed in thermal contact with thecenter of the heating element 572. A second thermocouple 574 may also beprovided in the opposing jaw for measuring the tissue temperature. Thesethermocouples are connected to the inputs of the processor/dataacquisition system 564. As the jaws are heated, the processor/dataacquisition system 564 collects temperature data and translates it tothe control algorithm 566. In a prototypical version, a ProportionalIntegral Derivative (PID) control algorithm is implemented in VisualBasic on a laptop for controlling the power supply output voltage. In acommercial design, the laptop and data acquisition functions will beimplemented in the power supply using a microcomputer and A/D and CJCchips, and the algorithm will be written in C or C++.

The advantages of the active feedback system as seen in FIG. 33A includethe ability to maintain optimal temperatures for sealing and cuttingregardless of tissue type or geometry. Furthermore, the ability toautomatically adjust power delivered to the heating element to minimizethe initial preheat time, followed by a lower power setting to form theweld reduces the overall operation time. Moreover the systemautomatically adjusts for different vessel diameters. Furthermore, thetemperature waveform may be used to determine the endpoint, orcompletion of the weld. The current method of waiting until severedvessels dropped from the jaws may result in longer than necessary weldtimes and unnecessary sticking and charring.

Tissue Welder with Resistance Welding Capability

During certain procedures such as vessel harvesting, devices of thepresent invention may inadvertently cause avulsion of incident vessels.More generally, blunt dissection, mechanical cutting of surroundingtissue, or incomplete tissue welding or other cautery may result inbleeding within the internal cavity. The present invention alsoencompasses supplemental heaters which may be used to stop such bleedingby creating “spot welds,” or localized areas of cauterized tissue byresistive heating of the tissue.

For example, FIGS. 34A, 34B, 35A, 35B, 36A, 36B, and 37 illustrate anumber of designs of tissue welder jaws having localized heaters orwelders on the distal end of one of the jaws. In general, the surfacearea per length of each of the resistance welders is larger than thesurface area per length of the associated heating element for weldingtissue so that a wider distribution of heat can be applied at thatpoint.

FIGS. 34A-34B illustrate a set of jaws 580, including a hot jaw 581which has a heating element 582 (i.e., for welding and/or severing) onits inside or jaw-facing surface, as described above. A separate circuitenergizes a flat ribbon heater 584 on the distal tip of the hot jaw 581for resistance welding. The separate activation circuit helps preventthermal damage to the heating element 582 which otherwise would beactivated along with the ribbon heater 584. Further, the separatecircuit has user controls by clearly differentiating between tissuewelding and resistance welding.

FIGS. 35A-35B illustrate a set of jaws 590, including a hot jaw 591which has a heating element 592. A flat ribbon heater 594 is provided onthe distal tip of the hot jaw 591 and is connected in series with theheating element 592. The ribbon heater 594 increases the surface area ofthe heating element 592 in contrast with a straight wire.

FIGS. 36A-36B illustrate a set of jaws 600, including a hot jaw 601which has a heating element 602 on its inside face. The distal end ofthe hot jaw 601 includes a shaped wireform heater 604 connected inseries with the heating element 602 which provides the ability tocauterize small areas of tissue in contact with the distal jaw tip whenthe heating element is activated. The serpentine band pattern of theheater 604 increases the length of exposed heater wire on the distalface of the jaw 601, and thus increases the amount of energy that can bedelivered to the tissue from the surface in contrast with a portion ofstraight wire as is seen in earlier embodiments.

Finally, FIG. 37 illustrates a still further set of tissue welding jaws610 including a hot jaw 611 having a heating element 612 thereon.Instead of the heating element 612 terminating at the distal tip of thejaw 611, it extends farther around the outside of the jaw and includes awidened pad 614 for resistance welding. Because the pad 614 or flatelectrode is exposed on the outside of the jaw, it can be more easilypositioned against the target tissue. A source of power and a separatefoot switch 616 for activating one or both of the circuits is shown.

In an alternative arrangement not specifically illustrated, a monopolarRF welder may be implemented using any of the previously describedconfigurations. More particularly, the tissue welding device may bedisconnected from the DC power supply and connect to an RF power source(such as a bovie unit) prior to resistance welding. The existing heatingelement circuit delivers the RF energy to the tissue, and the returnpath is through the patient's grounding path. Alternatively, both DC andRF power sources may be connected to the device, and a separate controlallows the user to switch between the two as desired.

It will also be appreciated by those of skill in the relevant art thatvarious modifications or changes may be made to the examples andembodiments described without departing from the intended scope of theinvention. In this regard, the particular embodiments of the inventiondescribed herein are to be understood as examples of the broaderinventive concept disclosed.

1. A surgical apparatus for welding and severing tissue, comprising:first and second relatively movable elongated jaws having jaw-facingsurfaces; an elongated shaft having the first and second relativelymovable jaws attached to a distal end thereof; a first heating elementfor welding tissue provided on the jaw-facing surface of the first jaw,the first heating element being adapted to heat up to a firsttemperature upon application of power; and a second heating element forsevering tissue also provided on the jaw-facing surface of the firstjaw, the second heating element being adapted to heat up to a secondtemperature greater than the first temperature upon application ofpower.
 2. The apparatus of claim 1, wherein the first heating elementhas a lower electrical resistance than the second heating element. 3.The apparatus of claim 1, wherein the first heating element has a widerprofile than the second heating element in a plane transverse to thedirection of elongation of the first jaw.
 4. The apparatus of claim 1,wherein the first heating element has a lower profile relative to thesecond heating element in a direction toward the second jaw.
 5. Theapparatus of claim 1, wherein the second heating element extendsgenerally centrally along the jaw-facing surface of the first jaw, andwherein the first heating element comprises at least two weldingmembers, one each on either side of the second heating element.
 6. Theapparatus of claim 5, wherein the at least two welding members areformed by a bifurcated segment of a one-piece heating element, theseparated portions in the bifurcated segment being connected in parallelto a source of power.
 7. The apparatus of claim 6, wherein the first andsecond heating elements are connected in series to a common source ofpower such that a current passing through one of the pair of weldingmembers is about one half the current passing through the second heatingelement.
 8. The apparatus of claim 5, wherein each of the weldingmembers comprises a strip of material having a generally flat jaw-facingsurface defining a lateral width, and wherein the second heating elementdefines a cylindrical jaw-facing surface having a lateral width smallerthan that of either of the welding members.
 9. The apparatus of claim 1,wherein the second jaw includes no heating elements such that the firstjaw is a “hot” jaw, and the second jaw is a “cold” jaw.
 10. Theapparatus of claim 1, further including a third heating element forwelding tissue also provided on the jaw-facing surface of the first jaw,the third heating element being adapted to heat up to a temperature uponapplication of power that is lower than the second temperature.
 11. Theapparatus of claim 1, further including a control handle connected to aproximal end of the elongated shaft and a control actuator mounted onthe handle for alternately separating and bringing together thejaw-facing surfaces of the elongated jaws, and a force-limitinginterface between the control actuator and the elongated jaws forlimiting the magnitude of closing force of the jaws.
 12. The apparatusof claim 1, wherein the first jaw comprises a ceramic material having athermal conductivity of less than 5.0 W/m-K.
 13. The apparatus of claim12, wherein the first jaw comprises an inner member covered with theceramic material.
 14. The apparatus of claim 13, wherein the innermember of the first jaw does not form a part of any electricalconduction path leading to either the first or second heating elements.15. (canceled)
 16. (canceled)
 17. A surgical apparatus for welding andsevering tissue, comprising: first and second relatively movableelongate jaws having jaw-facing surfaces; an elongated shaft having thefirst and second relatively movable jaws attached to a distal endthereof; a first heating element for welding tissue provided on thejaw-facing surface of one of the first or second jaws; a second heatingelement for severing tissue provided on the jaw-facing surface of one ofthe first or second jaws; and an electrical circuit path within thesurgical apparatus including a portion extending along the elongatedshaft and through the first and second heating elements in series,wherein upon application of current through the electrical circuit path,the first heating element heats up to a first temperature and the secondheating element heats up to a second temperature greater than the firsttemperature.
 18. The apparatus of claim 17, wherein the second heatingelement is provided on the jaw-facing surface of the second jaw, whereinthe first heating element has a wider profile than the second heatingelement in a plane transverse to the direction of elongation of thefirst jaw.
 19. The apparatus of claim 17, wherein the first heatingelement has a lower electrical resistance than the second heatingelement.
 20. The apparatus of claim 17, further including a controlhandle connected to a proximal end of the elongated shaft and a controlactuator mounted on the handle for alternately separating and bringingtogether the jaw-facing surfaces of the elongated jaws, and aforce-limiting interface between the control actuator and the elongatedjaws for limiting the magnitude of closing force of the jaws.
 21. Asurgical method of severing a target tissue while welding the severedends, comprising: providing a surgical apparatus for welding andsevering tissue including a pair of jaws adapted to open and close uponthe target tissue, the jaws including first and second resistive heatingelements; closing the jaws upon a target tissue; electrically energizingthe first heating element to a first temperature and for a sufficientperiod of time to form a welded region in the target tissue; andelectrically energizing the second heating element to a secondtemperature greater than the first temperature to sever the targettissue within the welded region.
 22. The method of claim 21, wherein thestep of electrically energizing the second heating element is performedafter forming the weld in the target tissue.
 23. (canceled)